JP7559520B2 - Power Conversion Equipment - Google Patents

Description

The disclosure in this specification relates to a power conversion device.

Patent Document 1 discloses a vehicle equipped with an inverter that converts DC power into AC power and supplies it to a three-phase motor, and a control device that controls the inverter. The inverter has an arm circuit provided for each of the three phases. In these arm circuits, the switching elements on the power line side and the switching elements on the earth line side are connected in series with each other. The switching elements on the power line side in each arm circuit are connected in parallel with each other, and the switching elements on the earth line side in each arm circuit are connected in parallel with each other.

The control device performs three-phase ON control when a short circuit occurs in a switching element in the inverter. Three-phase ON control is a process that turns on all switching elements connected in parallel to the switching element in which a short circuit occurs.

JP 2009-195026 A

However, in the above-mentioned Patent Document 1, when the control device performs three-phase ON control, a current flows through the switching elements that are turned on by the three-phase ON control. For this reason, if the back electromotive force of the motor is relatively large, there is a concern that the current flowing through the switching elements in the ON state will become large and the inverter will generate heat. For example, it is thought that increasing the output of the motor will increase the back electromotive force of the motor, making the inverter more likely to generate heat.

The main objective of this disclosure is to provide a power conversion device that can suppress heat generation due to abnormalities in the power conversion unit.

The various aspects disclosed in this specification employ different technical means to achieve their respective objectives. Furthermore, the symbols in parentheses in the claims and in this section are merely examples showing the correspondence with the specific means described in the embodiments described below as one aspect, and do not limit the technical scope.

In order to achieve the above object, one disclosed aspect comprises:
A power conversion device (13) for converting power supplied from a power supply unit (11) to a motor (12) having a multi-phase winding (12a) from direct current to alternating current by a power conversion unit (30) having a multi-phase conversion circuit (31) connected to each of the multi-phase windings,
a reference control unit (S113, S114) for controlling the power conversion unit so that a phase difference (PD3) between currents flowing through windings of a plurality of phases becomes a reference value;
a phase change unit (S203 to S205, S401, S501, S502) that controls the power conversion unit so that, when an abnormality occurs in at least one conversion circuit, the phase difference between currents passed through windings by the remaining conversion circuits of at least two phases is set as an abnormality phase difference (PD2) and the abnormality phase difference is changed from a reference value to a changed value;
Equipped with
The phase change unit is
The power conversion device has a winding opening section (S401, S501, S502) that switches a winding switch (59) that connects a conversion circuit and a winding in an abnormality-occurring conversion circuit to an open state .
One disclosed aspect is a method for producing a cellular membrane comprising:
A power conversion device (13) for converting power supplied from a power supply unit (11) to a motor (12) having a multi-phase winding (12a) from direct current to alternating current by a power conversion unit (30) having a multi-phase conversion circuit (31) connected to each of the multi-phase windings,
a reference control unit (S113, S114) for controlling the power conversion unit so that a phase difference (PD3) between currents flowing through windings of a plurality of phases becomes a reference value;
a phase change unit (S203 to S205, S401, S501, S502) which, when an abnormality occurs in one of a first switch (33) connected to one end of a winding in the at least one-phase conversion circuit and a second switch (36) connected to the other end of the winding, determines that an abnormality has occurred in the at least one-phase conversion circuit, and controls the power conversion unit so that the phase difference in the abnormal state (PD2) between currents passed through the windings by the remaining at least two-phase conversion circuits is changed from a reference value to a changed value;
Equipped with
The phase change unit is
This power conversion device has a winding opening unit (S401, S501, S502) that transitions a winding switch (59) that connects at least one of a first switch and a second switch to a winding to an open state for a conversion circuit in which an abnormality has occurred.
One disclosed aspect is a method for producing a cellular membrane comprising:
A power conversion device (13) for converting power supplied from a power supply unit (11) to a motor (12) having a multi-phase winding (12a) from direct current to alternating current by a power conversion unit (30) having a multi-phase conversion circuit (31) connected to each of the multi-phase windings,
a reference control unit (S113, S114) for controlling the power conversion unit so that a phase difference (PD3) between currents flowing through windings of a plurality of phases becomes a reference value;
a phase change unit (S203 to S205, S401, S501, S502) that controls the power conversion unit so that, when an abnormality occurs in at least one conversion circuit, the phase difference between currents passed through windings by the remaining conversion circuits of at least two phases is set as an abnormality phase difference (PD2) and the abnormality phase difference is changed from a reference value to a changed value;
Equipped with
The phase change unit is a power conversion device that controls the power conversion unit so that the abnormal phase difference is changed from a reference value to a changed value when the motor rotation speed (Nm) is equal to or lower than a predetermined rotation threshold value (Nth).

If an abnormality occurs in at least one phase of the conversion circuit and the motor is driven by at least two remaining phases of the conversion circuit, there is a concern that if the phase difference during the abnormality remains at the reference value, the rotating magnetic field of the motor will be in an unsuitable state for managing the back electromotive force of the motor. In this case, it is considered difficult to appropriately manage the back electromotive force of the motor.

In contrast, according to the above aspect, when an abnormality occurs in at least one conversion circuit and the motor is driven by the remaining conversion circuits of at least two phases, the phase difference during the abnormality is changed from the reference value to a changed value. In this configuration, the changed value is set to a value that improves the state of the rotating magnetic field of the motor, making it easier to manage the back electromotive force of the motor. If the back electromotive force of the motor can be properly managed, it becomes less likely that an overcurrent will flow in the power conversion unit due to the back electromotive force of the motor, causing the power conversion unit to heat up. Therefore, heat generation due to an abnormality in the power conversion unit can be suppressed.

FIG. 2 is a diagram showing the configuration of a drive system according to the first embodiment. FIG. 2 is a block diagram showing the electrical configuration of a control device. FIG. 4 is a diagram showing the relationship between current and magnetic field in a motor. 4A and 4B are diagrams for explaining a rotating magnetic field generated by three-phase control. 13 is a diagram for explaining a rotating magnetic field when a phase difference PD2 in two-phase control is 120 degrees. FIG. 13 is a diagram for explaining a rotating magnetic field when a phase difference PD2 in two-phase control is 60 degrees. FIG. 13 is a diagram for explaining a rotating magnetic field when a phase difference PD2 in two-phase control is 30 degrees. FIG. 11 is a diagram for explaining a rotating magnetic field when a phase difference PD2 in two-phase control is 90 degrees. FIG. 13 is a diagram for explaining a rotating magnetic field when a phase difference PD2 in two-phase control is 180 degrees. FIG. FIG. 4 is a diagram showing the relationship between motor rotation speed and torque for three-phase control and two-phase control. 4 is a flowchart showing a procedure of an inverter control process. 11 is a flowchart showing the procedure of a closing process. 11 is a flowchart showing the procedure of an opening process. FIG. 4 is a block diagram showing the electrical configuration of a current command unit. FIG. 11 is a diagram showing a change in motor torque when an inverter abnormality occurs. FIG. 4 is a diagram showing a change in the motor rotation speed when an inverter abnormality occurs. FIG. 13 is a diagram showing the configuration of a drive system according to a second embodiment. 11 is a flowchart showing the procedure of a closing process. 11 is a flowchart showing the procedure of an opening process. FIG. 13 is a block diagram showing an electrical configuration of a current command unit in a third embodiment. FIG. 13 is a block diagram showing an electrical configuration of a current command unit in a fourth embodiment. FIG. 13 is a diagram showing the configuration of another drive system.

Below, several embodiments for implementing the present disclosure will be described with reference to the drawings. In each embodiment, parts corresponding to matters described in the preceding embodiment may be given the same reference numerals, and duplicated descriptions may be omitted. In each embodiment, when only a part of the configuration is described, other previously described embodiments may be applied to the other parts of the configuration. In addition to combinations of parts that are specifically specified as being possible in each embodiment, it is also possible to partially combine embodiments even if not specified, as long as there is no particular problem with the combination.

First Embodiment
1 is mounted on a vehicle such as an electric vehicle (EV), a hybrid vehicle (HV), a fuel cell vehicle, etc. The drive system 10 has a battery 11, a motor 12, and a power conversion device 13. The drive system 10 is a system that drives the motor 12 to drive the drive wheels of the vehicle.

The battery 11 is a DC voltage source composed of a chargeable and dischargeable secondary battery, and corresponds to a power supply unit that supplies power to the motor 12 via the power conversion device 13. The secondary battery is, for example, a lithium-ion battery or a nickel-metal hydride battery. The battery 11 supplies a high voltage (for example, several hundred volts) to the inverter 30.

The motor 12 is a multi-phase AC motor, for example a three-phase AC rotating electric machine. The motor 12 has three phases: U-phase, V-phase, and W-phase. The motor 12 functions as an electric motor that is a driving source for the vehicle. The motor 12 functions as a generator during regeneration. The motor 12 has windings 12a that form an armature, and permanent magnets that form a field magnet. In this motor 12, the rotor is formed including the permanent magnets, and the stator is formed including the windings 12a. The motor 12, which is a three-phase motor, has three-phase windings 12a. The three-phase windings 12a correspond to multiple phase windings. The motor 12 is also sometimes called a motor generator or an electric motor.

In the motor 12, the windings 12a of the U-phase, V-phase, and W-phase are arranged to be offset by a predetermined angle. For example, as shown in FIG. 3, the windings 12a of the U-phase, V-phase, and W-phase are arranged to be offset by 120 degrees.

The power conversion device 13 shown in FIG. 1 performs power conversion between the battery 11 and the motor 12. The power conversion device 13 has a smoothing capacitor 21, an inverter 30, and a control device 40.

The smoothing capacitor 21 smoothes the DC voltage supplied from the battery 11. The smoothing capacitor 21 is connected to a P line 25, which is a high-potential power line, and an N line 26, which is a low-potential power line. The P line 25 is connected to the positive electrode of the battery 11, and the N line 26 is connected to the negative electrode of the battery 11. The positive electrode of the smoothing capacitor 21 is connected to the P line 25 between the battery 11 and the inverter 30. The negative electrode of the smoothing capacitor 21 is connected to the N line 26 between the battery 11 and the inverter 30. The smoothing capacitor 21 is connected in parallel to the battery 11. In the power conversion device 13, the P line 25 and the N line 26 are formed by bus bars or the like.

In the power conversion device 13, a switch 22 is provided between the smoothing capacitor 21 and the battery 11. The switch 22 connects the smoothing capacitor 21 and the battery 11 so that electricity can flow between them, and corresponds to a power switch. The switch 22 is formed of a switch or relay that can be switched between an open state and a closed state, and is provided on each of the P line 25 and the N line 26. In the P line 25, the switch 22 is provided between the positive electrode of the battery 11 and the positive electrode of the smoothing capacitor 21, and in the N line 26, the switch 22 is provided between the negative electrode of the battery 11 and the negative electrode of the smoothing capacitor 21. When the switch 22 is in the closed state, the battery 11 is electrically connected to the smoothing capacitor 21 and the inverter 30. When the switch 22 is in the open state, the battery 11 is electrically disconnected from the smoothing capacitor 21 and the inverter 30.

The switch 22 is basically in a closed state when a vehicle switch such as an ignition switch is on, and in an open state when the vehicle switch is off. For example, when the vehicle is running, the switch 22 is basically in a closed state. The switch 22 is sometimes referred to as a system main relay or SMR. The closed state of the switch 22 is sometimes referred to as a conductive state, and the open state is sometimes referred to as a cut-off state. Furthermore, when the switch 22 is in a closed state, the battery 11 and the smoothing capacitor 21 are in a conductive state, and when the switch 22 is in an open state, the continuity between the battery 11 and the smoothing capacitor 21 is cut off.

The switch 22 is provided with a drive unit that drives the switch 22 to open and close. The switch 22 and the control device 40 are electrically connected. The control device 40 controls the drive of the drive unit to cause the switch 22 to perform an opening or closing operation. The control device 40 drives the switch 22 to open and close so that each switch 22 provided on the P line 25 and the N line 26 is opened and closed collectively.

In this embodiment, the switch 22 is included in the power conversion device 13, but the switch 22 does not have to be included in the power conversion device 13. For example, the switch 22 may be provided between the power conversion device 13 and the battery 11. The switch 22 may also be provided only in the P line 25. In other words, the switch 22 only needs to be provided in at least the P line 25 of the P line 25 and the N line 26.

The power conversion device 13 is provided with a battery voltage sensor 23 and a capacitor voltage sensor 24. The battery voltage sensor 23 is a sensor that detects the voltage of the battery 11, and outputs a detection signal corresponding to the voltage of the battery 11 to the control device 40. The battery voltage sensor 23 is provided between the battery 11 and the smoothing capacitor 21, and is connected to each of the P line 25 and the N line 26. The capacitor voltage sensor 24 is a sensor that detects the voltage of the smoothing capacitor 21, and outputs a detection signal corresponding to the voltage of the smoothing capacitor 21 to the control device 40. The capacitor voltage sensor 24 is provided between the smoothing capacitor 21 and the inverter 30, and is connected to each of the P line 25 and the N line 26.

The inverter 30 is a DC-AC conversion circuit. The inverter 30 connects the battery 11 and the motor 12 via the switch 22. The inverter 30 performs power conversion to convert the power supplied from the battery 11 to the motor 12 from DC to AC. The inverter 30 is a three-phase inverter, and performs power conversion for each of the three phases. The inverter 30 corresponds to a power conversion unit. The inverter 30 converts DC voltage to AC voltage in response to switching control by the control device 40 and outputs the voltage to the motor 12. The motor 12 operates to generate a predetermined rotational torque in response to the AC voltage from the inverter 30. During regenerative braking of the vehicle, the inverter 30 converts the AC voltage generated by the motor 12 in response to rotational force from the drive wheels into DC voltage in response to switching control by the control device 40, and outputs the voltage to the battery 11 and the smoothing capacitor 21. The inverter 30 performs bidirectional power conversion between the battery 11 and the smoothing capacitor 21 and the motor 12.

The inverter 30 has a three-phase conversion circuit 31. The conversion circuit 31 performs power conversion for one phase. A conversion circuit 31 is provided for each of the U phase, V phase, and W phase. These conversion circuits 31 are connected in parallel to the motor 12. The conversion circuit 31 is an H-bridge circuit. In the inverter 30, three H-bridge circuits for three phases are connected in parallel.

The conversion circuit 31 has a first arm circuit 32 and a second arm circuit 35. These arm circuits 32, 35 are provided in the U-phase, V-phase, and W-phase, respectively. The first arm circuit 32 is connected to one end of the winding 12a, and the second arm circuit 35 is connected to the other end of the winding 12a. The first arm circuit 32 and the second arm circuit 35 are connected via the winding 12a. Both of the arm circuits 32, 35 are laid across the P line 25 and the N line 26. The P line 25 connects the positive electrode side of the battery 11, the high potential side of the first arm circuit 32, and the high potential side of the second arm circuit 35. The N line 26 connects the negative electrode side of the battery 11, the low potential side of the first arm circuit 32, and the low potential side of the second arm circuit 35. The first arm circuit 32 may be referred to as the first leg, and the second arm circuit 35 may be referred to as the second leg.

The first arm circuit 32 has an upper arm 32a and a lower arm 32b. The upper arm 32a and the lower arm 32b are connected in series between the P line 25 and the N line 26, with the upper arm 32a on the P line 25 side. The connection point between the upper arm 32a and the lower arm 32b is connected to the winding 12a of the corresponding phase in the motor 12 via an output line 27a. The first arm circuit 32 and the output line 27a are provided for each of the U phase, V phase, and W phase of the motor 12. The first arm circuit 32 has three upper arms 32a and three lower arms 32b.

The arms 32a and 32b each have an arm switch 33 and a diode 34. The arm switch 33 is formed of a switching element such as a semiconductor element. This switching element is a transistor having a gate, such as an IGBT or MOSFET. In this embodiment, for example, the arm switch 33 is formed of an n-channel IGBT. The diode 34 is a reflux diode and is connected in inverse parallel to the arm switch 33. In the arms 32a and 32b, the cathode of the diode 34 is connected to the collector of the arm switch 33, and the anode is connected to the emitter. In the arms 32a and 32b, the arm switch 33 and the diode 34 may be formed of one semiconductor element or multiple semiconductor elements.

The second arm circuit 35 has the same configuration as the first arm circuit 32. The second arm circuit 35 has an upper arm 35a and a lower arm 35b. The upper arm 35a and the lower arm 35b are connected in series between the P line 25 and the N line 26, with the upper arm 35a on the P line 25 side. The connection point between the upper arm 35a and the lower arm 35b is connected to the winding 12a of the corresponding phase in the motor 12 via an output line 27b. The second arm circuit 35 and the output line 27b are provided for each of the U phase, V phase, and W phase of the motor 12. The second arm circuit 35 has three upper arms 35a and three lower arms 35b.

The arms 35a and 35b of the second arm circuit 35 have the same configuration as the arms 32a and 32b of the first arm circuit 32. The arms 35a and 35b each have an arm switch 36 and a diode 37. The arm switch 36 is formed of a switching element such as a semiconductor element. This switching element is a transistor having a gate, such as an IGBT or MOSFET, like the arm switch 33. In this embodiment, for example, the arm switch 36 is formed of an n-channel IGBT. The diode 37 is a reflux diode and is connected in inverse parallel to the arm switch 36. In the arms 35a and 35b, the cathode of the diode 37 is connected to the collector of the arm switch 36, and the anode is connected to the emitter. In the arms 35a and 35b, the arm switch 36 and the diode 37 may be formed of one semiconductor element or multiple semiconductor elements.

In the inverter 30, the portion having the first arm circuits 32 of each of the three-phase conversion circuits 31 constitutes the first inverter section 38. In the inverter 30, the portion having the second arm circuits 35 of each of the three-phase conversion circuits 31 constitutes the second inverter section 39. The first inverter section 38 and the second inverter section 39 are connected to each other via the winding 12a of the motor 12, the P line 25, and the N line 26.

In the first inverter section 38, the portion having the upper arms 32a of the first arm circuits 32 for three phases constitutes the first upper arm group 38a. In the first inverter section 38, the portion having the lower arms 32b of the first arm circuits 32 for three phases constitutes the first lower arm group 38b. In the second inverter section 39, the portion having the upper arms 35a of the second arm circuits 35 for three phases constitutes the second upper arm group 39a. In the second inverter section 39, the portion having the lower arms 35b of the second arm circuits 35 for three phases constitutes the second lower arm group 39b.

In the conversion circuit 31, multiple arm switches 33, 36 are connected to each of the U-phase, V-phase, and W-phase windings 12a. Two arm switches 33 of the first arm circuit 32 and two arm switches 36 of the second arm circuit 35 are connected to the one-phase winding 12a. The arm switches 33, 36 correspond to conversion switches. Four conversion switches are connected to the one-phase winding 12a. The arm switch 33 of the first arm circuit 32 corresponds to the first switch, and the arm switch 36 of the second arm circuit 35 corresponds to the second switch.

The smoothing capacitor 21 is connected in parallel to the first arm circuit 32 and the second arm circuit 35 of each of the U-phase, V-phase, and W-phase. The smoothing capacitor 21 is connected to the arm switches 33 and 36 of the arm circuits 32 and 35 so that electricity can be conducted therethrough. The smoothing capacitor 21 corresponds to a capacitor.

The control device 40 is, for example, an ECU, and controls the operation of the inverter 30. ECU is an abbreviation for Electronic Control Unit. The control device 40 is mainly composed of a microcomputer (hereinafter, referred to as a microcomputer) equipped with, for example, a processor, memory, I/O, and a bus connecting these. The control device 40 executes various processes related to the operation of the inverter 30 by executing a control program stored in the memory. The memory referred to here is a non-transitory tangible storage medium that non-temporarily stores programs and data that can be read by a computer. The non-transitory tangible storage medium is realized by a semiconductor memory, a magnetic disk, or the like.

The control device 40 generates a drive command using signals input from a higher-level ECU such as an integrated ECU mounted on the vehicle and signals input from various sensors such as the rotation sensor 29. The control device 40 then causes the arm switches 33, 36 to perform on-drive and off-drive in response to this drive command. The arm switches 33, 36 can transition between an on state and an off state, transitioning to the on state when driven on and transitioning to the off state when driven off. For the arm switches 33, 36, the on state corresponds to a closed state and the off state corresponds to an open state.

Various sensors, such as a battery voltage sensor 23, a capacitor voltage sensor 24, a current sensor 28, and a rotation sensor 29, are electrically connected to the control device 40. These sensors 23, 24, 28, and 29 are included in the drive system 10. Of these sensors 23, 24, 28, and 29, the voltage sensors 23 and 24 and the current sensor 28 are included in the power conversion device 13.

The current sensor 28 is a current detection unit that detects the current flowing through the motor 12. The current sensor 28 outputs a detection signal corresponding to the current flowing through each of the three-phase windings 12a to the control device 40. The current sensor 28 is provided, for example, for at least one of the output lines 27a and 27b. The current sensor 28 detects the current flowing through the winding 12a by detecting the current flowing through the output lines 27a and 27b. The current sensor 28 discretely samples the current flowing through the winding 12a at a predetermined sampling period and outputs a discrete signal as a detection signal. The current flowing through the winding 12a is sometimes referred to as an armature current.

The rotation sensor 29 is provided on the motor 12 and is a rotation detection unit that detects the rotation speed of the motor 12. The rotation sensor 29 outputs a detection signal corresponding to the rotation speed of the motor 12 to the control device 40. The rotation sensor 29 is configured to include, for example, an encoder and a resolver.

The control device 40 shown in FIG. 2 performs vector control of the motor 12 via the inverter 30. In vector control, the three-phase AC coordinates represented by the U, V, and W phases are converted into dq coordinates represented by the d and q axes. The dq coordinates are rotational coordinates defined by the d and q axes, for example, with the d axis being the direction from the south pole of the rotor to the north pole, and the q axis being the direction perpendicular to the d axis.

The control device 40 has the following functional blocks: a current command unit 41, a three-phase to two-phase conversion unit 42, a d-axis subtraction unit 43, a q-axis subtraction unit 44, a current control unit 45, and a two-phase to three-phase conversion unit 46. These functional blocks may be configured as hardware using at least one IC or the like, or may be executed by a combination of software execution by a processor and hardware.

The three-phase to two-phase conversion unit 42 receives the U-phase current Iu, V-phase current Iv, and W-phase current Iw detected by the current sensor 28. These phase currents Iu, Iv, and Iw are detection values of the currents that actually flow through the windings 12a of each phase in the motor 12. The control device 40 has a current acquisition unit that acquires the phase currents Iu, Iv, and Iw using the detection signal from the current sensor 28. This current acquisition unit may be included in the three-phase to two-phase conversion unit 42.

The motor rotation speed Nm detected by the rotation sensor 29 is input to the three-phase to two-phase conversion unit 42. This motor rotation speed Nm is a detected value indicating the actual rotation speed of the motor 12. The motor rotation speed Nm is, for example, the number of rotations of the motor 12 per unit time, and is a value indicating the rotation speed.

The three-phase to two-phase conversion unit 42 converts the U-phase current Iu, V-phase current Iv, and W-phase current Iw of the three-phase AC coordinate system into the dq coordinate system to calculate the d-axis current Id and the q-axis current Iq of the dq coordinate system. The d-axis current Id is a component in the d-axis direction in the dq coordinate system, and the q-axis current Iq is a component in the q-axis direction in the dq coordinate system. The three-phase to two-phase conversion unit 42 calculates the d-axis current Id and the q-axis current Iq using the motor rotation speed Nm in addition to the phase currents Iu, Iv, and Iw. For example, the three-phase to two-phase conversion unit 42 converts the phase currents Iu, Iv, and Iw into the dq coordinate system based on the motor rotation speed Nm to calculate the d-axis current Id and the q-axis current Iq. The d-axis current Id and the q-axis current Iq are input to the d-axis subtraction unit 43.

The three-phase to two-phase conversion unit 42 corresponds to a coordinate conversion unit. The d-axis current Id and the q-axis current Iq are sometimes referred to as the actual d-axis current and the actual q-axis current, since they are actual currents obtained by performing coordinate conversion on the detected values of the phase currents Iu, Iv, and Iw. Furthermore, the d-axis current Id is sometimes referred to as the field current, and the q-axis current is sometimes referred to as the drive current. The three-phase to two-phase conversion unit 42 is sometimes referred to as the uvw/dq conversion unit.

The current command unit 41 sets the target values for the d-axis current Id and the q-axis current Iq as the d-axis current command value Id* and the q-axis current command value Iq*, respectively. The command values Id* and Iq* set by the current command unit 41 are input to the d-axis subtraction unit 43 as the d-axis current command value Id* and to the q-axis subtraction unit 44 as the q-axis current command value Iq*. The current command unit 41 receives a torque command value as a signal from a higher-level ECU as the rotational torque to be generated by the motor 12. The current command unit 41 sets the command values Id* and Iq* according to the torque command value when, for example, power is being supplied from the battery 11 to the motor 12.

The d-axis subtraction unit 43 calculates the deviation between the d-axis current command value Id* and the d-axis current Id as the d-axis current deviation. The q-axis subtraction unit 44 calculates the deviation between the q-axis current command value Iq* and the q-axis current Iq as the q-axis current deviation. These d-axis current deviation and q-axis current deviation are input to the current control unit 45.

The current control unit 45 calculates the d-axis voltage command value Vd* and the q-axis voltage command value Vq* in the dq coordinate system so that the d-axis current deviation and the q-axis current deviation become zero. The current control unit 45 performs feedback control to calculate the d-axis voltage command value Vd* and the q-axis voltage command value Vq* so that the d-axis current Id matches the d-axis current command value Id* and the q-axis current Iq matches the q-axis current command value Iq*. The current control unit 45 performs, for example, PI control as the feedback control. The d-axis voltage command value Vd* and the q-axis voltage command value Vq* are input to the 2-phase to 3-phase conversion unit 46.

The two-phase to three-phase conversion unit 46 converts the d-axis voltage command value Vd* and the q-axis voltage command value Vq* in the dq coordinate system into three-phase AC coordinates to calculate the U-phase voltage command value Vu*, the V-phase voltage command value Vv*, and the W-phase voltage command value Vw* in the three-phase coordinate system. These voltage command values Vu*, Vv*, and Vw* are voltage values to be output to each of the three-phase windings 12a, and are information included in the drive command. A drive command including these voltage command values Vu*, Vv*, and Vw* is input to the inverter 30. The two-phase to three-phase conversion unit 46 is sometimes referred to as a dq/uvw conversion unit.

Next, we will explain the rotating magnetic field MFR generated by the motor 12.

As shown in FIG. 3, in the motor 12, magnetic fields MFu, MFv, and MFw are generated by the currents Iu, Iv, and Iw. In the motor 12, the U-phase winding 12a, the V-phase winding 12a, and the W-phase winding 12a are arranged with a 120-degree offset from each other. As a result, the U-phase magnetic field MFu generated by the U-phase current Iu, the V-phase magnetic field MFv generated by the V-phase current Iv, and the W-phase magnetic field MFw generated by the W-phase current Iw are all shifted by 120 degrees from each other. In FIG. 3 and other figures, the magnetic fields MFu, MFv, and MFw are illustrated as vectors with arrows.

When no abnormality occurs in the inverter 30, the control device 40 performs three-phase control of the inverter 30. In three-phase control, the three-phase currents Iu, Iv, and Iw are controlled. In three-phase control, as shown in FIG. 4, the inverter 30 is controlled so that the phase difference PD3 of the currents Iu, Iv, and Iw, which are three-phase currents, is 120 degrees. This 120 degrees corresponds to the reference value. When the phase difference PD3 of the currents Iu, Iv, and Iw becomes 120 degrees, the phase difference of the magnetic fields MFu, MFv, and MFw also becomes 120 degrees. The synthetic magnetic field MFS, which is a combination of the magnetic fields MFu, MFv, and MFw, changes its direction depending on the phase of the currents Iu, Iv, and Iw. On the other hand, the magnitude of the synthetic magnetic field MFS is almost the same even if the phase of the currents Iu, Iv, and Iw changes, and is difficult to change. If the rotation locus of the composite magnetic field MFS caused by the phase change of the currents Iu, Iv, and Iw is called the rotating magnetic field MFR, the rotating magnetic field MFR will have a circular or nearly circular shape. In this embodiment, a circular or nearly circular shape is called a circular shape.

In the drive system 10, when the rotating magnetic field MFR is circular, the control device 40 can normally control the power conversion device 13. For example, the control device 40 can control the motor 12 so that the back electromotive force does not become too large. The control device 40 can also control the motor 12 so that torque ripple does not occur. In this way, the controllability of the power conversion device 13 by the control device 40 can be improved.

In the drive system 10, when the motor 12 is driven and rotated by the power supply from the battery 11 during vehicle running, etc., if an inverter abnormality occurs in the inverter 30, there is a concern that a secondary abnormality will occur along with the inverter abnormality. For example, inverter abnormalities include a short circuit abnormality in which the arm switches 33, 36 are unintentionally turned on, and an open circuit abnormality in which the arm switches 33, 36 are unintentionally turned off. When a short circuit abnormality occurs, the arm switches 33, 36 are thought to unintentionally transition to an on state and remain in the on state unintentionally. When an open circuit abnormality occurs, the arm switches 33, 36 are thought to unintentionally transition to an off state and remain in the off state unintentionally. In this embodiment, the arm switches 33, 36 are formed by switching elements in which a short circuit abnormality is more unlikely to occur than an open circuit abnormality.

When a short circuit or open circuit occurs in the inverter 30, there is a concern that a control failure will occur in which the arm switches 33, 36 do not operate according to the command of the control device 40. When a control failure occurs, secondary abnormalities are more likely to occur in the drive system 10. For example, when an overvoltage occurs in the auxiliary devices such as the voltage sensors 23, 24 and the smoothing capacitor 21 due to the back electromotive force of the motor 12, secondary abnormalities are more likely to occur in these auxiliary devices and the smoothing capacitor 21. When an overcurrent flows in the inverter 30 due to the back electromotive force of the motor 12, secondary abnormalities are more likely to occur in the inverter 30.

In this embodiment, when an abnormality occurs in one of the conversion circuits 31 in the inverter 30, the currents that the remaining two-phase conversion circuits 31 pass through the windings 12a are controlled by the control device 40. The control device 40 performs two-phase control to control the currents for the remaining two phases in which no abnormality occurs in the conversion circuit 31. Two-phase control is sometimes called abnormality control that is performed when an inverter abnormality occurs. In two-phase control, two-phase magnetic fields are generated by the currents of the remaining two phases, and the composite magnetic field MFS and the rotating magnetic field MFR are formed by the two-phase magnetic fields. With regard to two-phase control, it has been found through tests and the like that if the phase difference PD2 of the currents of the remaining two phases remains at 120 degrees as things stand, the rotating magnetic field MFR becomes elliptical. The fact that the rotating magnetic field MFR becomes elliptical means that the magnitude of the composite magnetic field MFS varies depending on the phase. The greater the flatness of the rotating magnetic field MFR, the greater the variation in the magnitude of the composite magnetic field MFS depending on the phase. The phase difference PD2 corresponds to the abnormality phase difference.

For example, if an abnormality occurs in the W-phase of the inverter 30 and the current to the W-phase winding 12a is stopped, the two-phase control controls the remaining U-phase current Iu and V-phase current Iv. In this two-phase control, as shown in FIG. 5, if the phase difference PD2 between the U-phase current Iu and the V-phase current Iv remains at 120 degrees, the rotating magnetic field MFR becomes elliptical.

In contrast, it has been found through testing etc. that when the phase difference PD2 in two-phase control is changed, the shape of the rotating magnetic field MFR changes. According to this finding, the rotating magnetic field MFR in this case is smaller for all phases compared to the rotating magnetic field MFR generated by three-phase control. Using as an example a case where the current supply to the W-phase winding 12a is stopped, the relationship between the phase difference PD2 between the remaining U-phase current Iu and V-phase current Iv and the shape of the rotating magnetic field MFR will be explained.

As shown in FIG. 6, when the phase difference PD2 in two-phase control is changed to 60 degrees, the rotating magnetic field MFR becomes circular, as in three-phase control. In this case, the magnitude of the resultant magnetic field MFS is consistent and does not vary depending on the phase. In this way, when the phase difference PD2 is 60 degrees, the variation in the magnitude of the resultant magnetic field MFS depending on the phase is smaller than when the phase difference PD2 is 120 degrees. On the other hand, the magnitude of the rotating magnetic field MFR is smaller than the magnitude of the rotating magnetic field MFR in three-phase control. Specifically, it is 1/√3.

As shown in FIG. 7, when the phase difference PD2 is changed to 30 degrees, the rotating magnetic field MFR becomes elliptical, similar to when the phase difference PD2 remains at 120 degrees. The rotating magnetic field MFR when the phase difference PD2 is 30 degrees has a smaller flattening ratio and is closer to a circle than when the phase difference PD2 remains at 120 degrees. Furthermore, the rotating magnetic field MFR when the phase difference PD2 is 30 degrees is smaller for all phases than the rotating magnetic field MFR generated by three-phase control.

As shown in FIG. 8, when the phase difference PD2 is changed to 90 degrees, the rotating magnetic field MFR becomes elliptical, as when the phase difference PD2 is changed to 30 degrees. The rotating magnetic field MFR when the phase difference PD2 is 90 degrees has a smaller flattening ratio and is closer to a circle than when the phase difference PD2 remains at 120 degrees and when the phase difference PD2 is 30 degrees. Furthermore, the rotating magnetic field MFR when the phase difference PD2 is 90 degrees is smaller for all phases than the rotating magnetic field MFR generated by three-phase control.

As shown in FIG. 9, when the phase difference PD2 is changed to 180 degrees, the rotating magnetic field MFR has a shape that extends in only one direction. When the phase difference PD2 is 180 degrees, the flattening of the rotating magnetic field MFR is even greater than when the phase difference PD2 remains at 120 degrees. In addition, when the phase difference PD2 is 180 degrees, the rotating magnetic field MFR is smaller for all phases compared to the rotating magnetic field MFR generated by three-phase control.

In this embodiment, the control device 40 performs two-phase control by setting the phase difference PD2 so that the flattening of the rotating magnetic field MFR is smaller and the shape is closer to a circle than when the phase difference PD2 remains at 120 degrees in two-phase control. For example, the control device 40 performs two-phase control by setting the phase difference PD2 to 60 degrees and changing the phase difference PD2 to 60 degrees. This 60 degrees corresponds to the change value. Note that a smaller flattening of the rotating magnetic field MFR means that the aspect of the rotating magnetic field MFR has been improved.

However, as mentioned above, the rotating magnetic field MFR generated by two-phase control is smaller than the rotating magnetic field MFR generated by three-phase control. Therefore, when the motor rotation speed Nm is in the high rotation range, the rotating magnetic field MFR generated by two-phase control may be insufficient, and the power conversion device 13 may not be able to drive the motor 12, which may cause a negative torque instead of a positive torque to be generated in the motor 12.

The high rotation range is a range where the motor rotation speed Nm is greater than a predetermined rotation threshold value Nth. The rotation threshold value Nth is a value of the motor rotation speed Nm at which no negative torque is generated in the motor 12 when two-phase control of the motor 12 is being performed by the power supplied from the battery 11. In this embodiment, the maximum value of the motor rotation speed Nm at which no negative torque is generated in the motor 12 is set as the rotation threshold value Nth. Therefore, the rotation threshold value Nth is the motor rotation speed Nm when the torque of the motor 12 is zero. For the motor 12, the state in which the torque is zero is referred to as zero torque. Positive torque is sometimes referred to as powering torque, and negative torque is sometimes referred to as regenerative torque.

As shown in FIG. 10, when three-phase control of motor 12 is performed with phase difference PD3 at 120 degrees, positive torque is generated in motor 12 even in a high rotation range greater than rotation threshold Nth. On the other hand, when two-phase control of motor 12 is performed with phase difference PD2 at 60 degrees, negative torque is likely to be generated in motor 12 in a high rotation range greater than rotation threshold Nth. In this case, the back electromotive force of motor 12 may cause overvoltage in the auxiliary equipment and smoothing capacitor 21. In addition, in this case, the back electromotive force of motor 12 may cause an overcurrent to flow through inverter 30, causing inverter 30 to heat up.

When the motor speed Nm is in the high rotation range, the control device 40 performs voltage increase control so that the voltage applied to the winding 12a increases to a higher value than in the case of three-phase control. In this voltage increase control, the inverter 30 is controlled so that the capacitor voltage Vc is higher than the battery voltage V0. The capacitor voltage Vc is the voltage across the smoothing capacitor 21. The battery voltage V0 is the voltage of the battery 11 and corresponds to the power supply voltage.

The control device 40 performs reactive power control and voltage drop control in addition to voltage increase control. In reactive power control, the inverter 30 is controlled so that the motor rotation speed Nm is smaller than in the high rotation range. In voltage drop control, the inverter 30 is controlled so that the capacitor voltage Vc drops to the battery voltage V0. When the motor rotation speed Nm is in the high rotation range, the control device 40 performs voltage increase control, voltage drop control, and reactive power control along with two-phase control. Note that reactive power control is sometimes referred to as rotation decrease control, which reduces the motor rotation speed Nm.

The control device 40 performs inverter control processing to control the inverter 30. Three-phase control, two-phase control, voltage increase control, voltage decrease control, and reactive power control are performed by the inverter control processing. The inverter control processing will be described with reference to the flowcharts of Figures 11 to 13. The control device 40 repeatedly executes the inverter control processing at a predetermined cycle. The control device 40 has the function of executing each step of the inverter control processing.

In FIG. 11, in step S101, it is determined whether an inverter abnormality has occurred. Here, it is determined whether there is an abnormality in the operation of the inverter 30 according to the drive command from the control device 40. For example, the detection signals of various sensors such as the current sensor 28 are compared with the drive command to the inverter 30, and the drive state of the inverter 30 is determined using the comparison result.

If no inverter abnormality has occurred, steps S111 to S114 are performed as normal processing. Of the normal processing, steps S113 and S114 are three-phase control processing that performs three-phase control. In the normal processing, in step S111, the d-axis current command value Id* is set according to the torque command value. In step S112, the q-axis current command value Iq* is set according to the torque command value. Note that the function of executing steps S111 and S112 is included in the current command unit 41.

Vu*=Vd*cos(θ)-Vq*sin(θ)...Formula 1
Vv*=Vd*cos(θ-120°)-Vq*sin(θ-120°)...Formula 2
Vw*=Vd*cos(θ+120°)−Vq*sin(θ+120°)…Formula 3
In the three-phase control process, in step S113, three-phase voltage commands are issued. Here, voltage command values Vu*, Vv*, and Vw* are calculated. For this calculation, for example, Equations 1 to 3 are used. Equation 1 In the formulas 2 to 3, θ is the phase difference between the three-phase currents Iu, Iv, and Iw and the three-phase voltages Vu, Vv, and Vw. The formulas 2 and 3 indicate that the reference value is 120 degrees. .

In step S114, the switches are driven. Here, a drive command is generated according to the voltage command values Vu*, Vv*, Vw*, and a command signal including this drive command is output to the inverter 30. For example, the voltage command values Vu*, Vv*, Vw* are compared with the carrier, and a pulse-shaped drive command is generated for each of the U-phase, V-phase, and W-phase. The carrier is a carrier wave such as a triangular wave, sawtooth wave, or rectangular wave. This drives the arm switches 33, 36 of the conversion circuit 31 individually for each of the U-phase, V-phase, and W-phase. Note that the function of the control device 40 that executes steps S113 and S114 corresponds to the reference control unit.

In the above step S101, if an inverter abnormality occurs, the process proceeds to step S102. In step S102, the phase in which an abnormality occurs in the inverter 30 is called the abnormal phase, and it is obtained which of the three phases is the abnormal phase. For example, for each of the U phase, V phase, and W phase, the detection signals of various sensors are compared with the drive command to the inverter 30 in the same manner as in step S101. Then, using the comparison result, it is determined whether or not there is an abnormality in the drive of the conversion circuit 31 for each of the U phase, V phase, and W phase. For example, it is determined whether or not a short circuit abnormality or an open circuit abnormality has occurred in the arm switches 33 and 36 in the conversion circuits 31 of the U phase, V phase, and W phase. Of the U phase, V phase, and W phase, the phase in which it is determined that an abnormality has occurred in the conversion circuit 31 is determined to be the abnormal phase. Note that if it is determined that an abnormality has occurred in the conversion circuit 31 for two or more phases, multiple phases are obtained as abnormal phases.

For the abnormal phase, it is determined whether a short circuit abnormality or an open circuit abnormality has occurred for all arm switches 33, 36 in the conversion circuit 31. For example, all arm switches 33, 36 in the conversion circuit 31 are driven individually, and the presence or absence and type of abnormality in the arm switches 33, 36 are obtained using the drive results. Of the arm switches 33, 36 in the conversion circuit 31 of the abnormal phase, the switch that is determined to have an abnormality is determined to be the abnormal switch. If it is determined that an abnormality has occurred in two or more arm switches 33, 36, there are two or more abnormal switches.

In step S103, it is determined whether or not two-phase control is to be performed. Here, it is determined whether or not there are two or more abnormal phases in the inverter 30. In other words, it is determined whether or not two-phase control can be performed. If there are two or more abnormal phases, it is determined that two-phase control cannot be performed, and the process proceeds to step S110. It is also determined whether or not there are multiple abnormal switches for the conversion circuit 31 of the abnormal phase. This also determines whether or not two-phase control can be performed. If there are two or more abnormal switches, it is also determined that two-phase control cannot be performed, and the process proceeds to step S110.

In step S110, a save process is performed. This save process is a process that does not perform either three-phase control or two-phase control on the motor 12. As a save process, for example, a stop process that stops the drive of the motor 12 is performed. In this stop process, an all-off process or an ASC process is performed. In the all-off process, an off command is output to all arm switches 33, 36 of the inverter 30. As a result, all arm switches 33, 36 in the inverter 30 except for the abnormal switch transition to the off state.

In the ASC process, the control device 40 performs active short circuiting on the inverter 30. Hereinafter, active short circuiting is referred to as ASC. Specifically, an OFF command is output to one of the upper arm groups 38a, 39a and the lower arm groups 38b, 39b, and an ON command is output to the other. As a result, all arm switches 33, 36 of one of the upper arm groups 38a, 39a and the lower arm groups 38b, 39b transition to the ON state, and all arm switches 33, 36 of the other transition to the OFF state. This state is referred to as the ASC state.

In step S103, if two-phase control is to be performed, the process proceeds to step S104. In step S104, the motor rotation speed Nm is acquired using the detection signal of the rotation sensor 29. In step S105, it is determined whether the motor rotation speed Nm is greater than a predetermined rotation threshold value Nth. As described above, the rotation threshold value Nth is the value of the motor rotation speed Nm at which the motor 12 has zero torque when two-phase control is being performed at the battery voltage V0. The rotation threshold value Nth is information acquired by testing, simulation, etc., and is stored in a storage unit such as a memory in the control device 40.

If the motor rotation speed Nm is not greater than the rotation threshold value Nth, the process proceeds to step S108, where the switch 22 is closed. Here, a close signal is output to the drive unit of the switch 22. As a result, if the switch 22 is in the open state, the switch 22 transitions to the closed state, and if the switch 22 is already in the closed state, the closed state is maintained. In either case, power is supplied from the battery 11 to the power conversion device 13 and the motor 12 via the switch 22.

In step S109, a closing process is performed. The closing process is described with reference to the flowchart shown in FIG. 12.

As shown in FIG. 12, in the closing process, steps S201 and S202 are performed as preparations for two-phase control. In the preparations, in step S201, a d-axis current command value Id* is set according to the torque command value. In step S202, a q-axis current command value Iq* is set according to the torque command value. The function of executing steps S201 and S202 is included in the current command unit 41.

In the closing process, steps S203 to S205 are two-phase control processes that perform two-phase control. In steps S203 to S205, the inverter 30 is controlled so that the current phase difference PD2 is changed from 120 degrees to 60 degrees for two of the three phases excluding the abnormal phase. The function of the control device 40 that executes the processes of steps S203 to S205 corresponds to the phase change unit. Also, changing the phase difference PD2 from 120 degrees to 60 degrees corresponds to changing the phase difference PD2 from a reference value to a changed value.

Vu*=Vd*cos(θ-βu)-Vq*sin(θ-βu)...Formula 4
Vv*=Vd*cos(θ-120°-βv)-Vq*sin(θ-120°-βv)...Formula 5
Vw*=Vd*cos(θ+120°-βw)-Vq*sin(θ+120°-βw)...Formula 6
In the two-phase control process, in step S203, two-phase voltage commands are issued. Here, voltage command values Vu*, Vv*, and Vw* are calculated in the same manner as in the three-phase control. However, in the two-phase control, the voltage command The values Vu*, Vv*, and Vw* are calculated using, for example, Equations 4 to 6. Similarly to Equations 1 to 3, θ in Equations 4 to 6 is expressed by the three-phase currents Iu, Iv, and Iw and the three-phase is the phase difference between the voltages Vu, Vv, and Vw. Similarly to the expressions 2 and 3, the expressions 5 and 6 indicate that the reference value is 120 degrees.

The values βu, βv, and βw in Equations 4 to 6 are values for changing the phase of the two-phase voltage so that the phase difference PD2 between the two-phase currents becomes 60 degrees in two-phase control. These βu, βv, and βw are set so that the phases to be changed for the two-phase currents are the same value. For example, if the abnormal phase in inverter 30 is the U-phase, βu, βv, and βw are set so that the V-phase current Iv is retarded by 30 degrees and the W-phase current Iw is advanced by 30 degrees. As described later, two-phase control is performed for the abnormal U-phase so that the U-phase current Iu does not flow, so βu, βv, and βw are set ignoring the phase of the U-phase current Iu. Note that βu, βv, and βw may be set so that the phase of the U-phase current Iu does not change.

For example, if the abnormal phase in inverter 30 is the V phase, βu, βv, and βw are set so that the W phase current Iw is retarded by 30 degrees and the U phase current Iu is advanced by 30 degrees. βu, βv, and βw are set while ignoring the phase of the V phase current Iv of the abnormal phase. For example, if the abnormal phase in inverter 30 is the W phase, βu, βv, and βw are set so that the U phase current Iu is retarded by 30 degrees and the V phase current Iv is advanced by 30 degrees. βu, βv, and βw are set while ignoring the phase of the W phase current Iw of the abnormal phase.

In step S204, the switches are driven. Here, drive commands are generated according to the voltage command values Vu*, Vv*, and Vw*. For example, similar to three-phase control, the voltage command values Vu*, Vv*, and Vw* are compared with the carrier, and pulse-shaped drive commands are generated for each of the U phase, V phase, and W phase. Note that, unlike three-phase control, the process of outputting a command signal including a drive command to the inverter 30 is performed in the next step S205.

In step S205, abnormal phase off drive is performed. Here, a drive command is generated for the abnormal phase of the inverter 30 to drive all arm switches 33, 36 except the abnormal switch in the conversion circuit 31 to off. Then, for only the abnormal phase, the drive command generated in step S204 is updated to the drive command generated in this step S205. Then, a command signal including a drive command for each of the U phase, V phase, and W phase is output to the inverter 30. As a result, in the conversion circuit 31 of the abnormal phase, all arm switches 33, 36 except the abnormal switch are switched to the off state. Therefore, the arm switches 33, 36 cut off the current to the winding 12a connected to the conversion circuit 31 of the abnormal phase. For the conversion circuit 31 of the two phases that are not abnormal, the arm switches 33, 36 are turned on and off according to the drive command.

The function of the control device 40 that executes the process of step S203 corresponds to the voltage command unit. The function of the control device 40 that executes the process of step S205 corresponds to the cutoff execution unit and the conversion opening unit.

In step S105, if the motor rotation speed Nm is greater than the rotation threshold Nth, the process proceeds to step S106, where the switch 22 is opened. Here, an open signal is output to the drive unit of the switch 22. As a result, if the switch 22 is in a closed state, the switch 22 transitions to an open state, and if the switch 22 is already in an open state, the open state is maintained. In either case, the power supply from the battery 11 to the power conversion device 13 and the motor 12 is cut off by the switch 22. Note that the function of the control device 40 that executes the process of step S106 corresponds to the open transition unit. Also, the rotation threshold Nth corresponds to the open threshold.

In step S107, the opening process is performed. The opening process will be described with reference to the flowchart shown in FIG. 13.

In the opening process shown in FIG. 13, steps S301 to S309 are first performed. In step S309, it is determined whether the motor rotation speed Nm is equal to or less than the rotation threshold value Nth. Then, steps S301 to S309 are repeatedly performed until the motor rotation speed Nm becomes equal to or less than the rotation threshold value Nth.

After the switch 22 is opened in step S106, the first steps S301 to S305 are the same as steps S201 to S205 of the closing process. For example, in step S301, the d-axis current command value Id* is set according to the torque command value, as in step S201 of the closing process. In step S302, the q-axis current command value Iq* is set according to the torque command value, as in step S202 of the closing process.

Steps S303 to S305 are two-phase control processes that perform two-phase control in the closing process. The two-phase control process in steps S303 to S305 is a process that is executed together with the voltage increase process described below. In steps S303 to S305, the inverter 30 is controlled so that the current phase difference PD2 is changed from 120 degrees to 60 degrees for two of the three phases excluding the abnormal phase. The function in the control device 40 that executes the processes in steps S303 to S305 corresponds to the opening control unit in the opening process.

In step S303, a two-phase voltage command is issued in the same manner as in step S203 of the closing process. In step S304, switch driving is performed in the same manner as in step S204 of the closing process. In step S305, abnormal phase off driving is performed in the same manner as in step S205 of the closing process.

In step S306, the capacitor mode is set. The capacitor mode is a mode in which the capacitor voltage Vc is used to set the current command values Id* and Iq*. Step S308 and step S302 from the second time onwards are voltage increase processing in which voltage increase control is performed in the capacitor mode. Step S308 and step S301 from the second time onwards are reactive power processing in which reactive power control is performed in the capacitor mode. In step S306, if the capacitor mode has not yet been set, a new capacitor mode is set. If the capacitor mode has already been set, the capacitor mode continues.

In step S302 from the second time onwards, the voltage change unit 53 is used to set the q-axis current command value Iq* according to the capacitor voltage Vc. In step S301 from the second time onwards, the reactive power change unit is used to set the d-axis current command value Id* according to the capacitor voltage Vc and the motor rotation speed Nm.

First, the voltage change unit 53 will be described. As shown in FIG. 14, the control device 40 has a voltage change unit 53. The voltage change unit 53 is a functional block included in the current command unit 41, and sets the q-axis current command value Iq* according to the capacitor voltage Vc, not the torque command value. The voltage change unit 53 calculates the q-axis current command value Iq* by feedback control so that the capacitor voltage Vc matches the capacitor command value Vc*.

The voltage change unit 53 has a capacitor subtraction unit 54 and a capacitor control unit 55. The capacitor subtraction unit 54 receives the capacitor command value Vc* read from the storage unit and the capacitor voltage Vc detected by the capacitor voltage sensor 24. The capacitor subtraction unit 54 calculates the deviation between the capacitor command value Vc* and the capacitor voltage Vc as the capacitor deviation. This capacitor deviation is input to the capacitor control unit 55.

The capacitor control unit 55 calculates the q-axis current command value Iq* so that the capacitor deviation becomes zero. The capacitor control unit 55 performs feedback control to calculate the q-axis current command value Iq* so that the capacitor voltage Vc matches the capacitor command value Vc*. The capacitor control unit 55 performs, for example, PI control as the feedback control. The q-axis current command value Iq* set by the capacitor control unit 55 is input to the q-axis subtraction unit 44. The capacitor subtraction unit 54 and the capacitor control unit 55 are functional blocks included in the voltage change unit 53.

Next, the reactive power change unit will be described. The control device 40 has a reactive power change unit (not shown). The reactive power change unit is a functional block included in the current command unit 41, and sets the d-axis current command value Id* according to the capacitor voltage Vc and the motor rotation speed Nm, rather than the torque command value. The reactive power change unit calculates the d-axis current command value Id* by feedback control so that the capacitor voltage Vc matches the capacitor command value Vc* and the motor rotation speed Nm matches the rotation threshold value Nth.

In the reactive power change unit, for example, the capacitor deviation is calculated, and the deviation between the motor rotation speed Nm and the rotation threshold value Nth is calculated as the motor deviation. Then, feedback control of the d-axis current command value Id* is performed so that both the capacitor deviation and the motor deviation become zero. For example, PI control is used as this feedback control. Then, the d-axis current command value Id* set in the reactive power change unit is input to the d-axis subtraction unit 43.

Returning to the explanation of FIG. 13, after the capacitor mode is set in step S306, various information is detected in step S307. For example, the capacitor voltage Vc is obtained using the detection signal of the capacitor voltage sensor 24. In addition, the motor rotation speed Nm is obtained using the detection signal of the rotation sensor 29.

In step S308, a predetermined capacitor upper limit value Vh is substituted for the capacitor command value Vc*. The capacitor upper limit value Vh is set, for example, according to the maximum allowable voltage or rated voltage of the smoothing capacitor 21. The capacitor upper limit value Vh is a value equal to or less than the inverter upper limit value of the inverter 30. On the other hand, the capacitor upper limit value Vh is a value greater than the battery voltage V0. The inverter upper limit value is the upper limit value of the voltage applied to the inverter 30, and is set, for example, according to the rated value or maximum allowable voltage of the inverter 30. The capacitor upper limit value Vh is information obtained by testing, simulation, etc., and is stored in a storage unit such as a memory in the control device 40.

The inverter upper limit value can also be referred to as the withstand voltage value of the inverter 30. The withstand voltage value of the inverter 30 is set to the withstand voltage value of the component or device with the lowest withstand voltage value in the inverter 30. For example, if the component with the lowest withstand voltage value in the inverter 30 is the arm switches 33 and 36, the withstand voltage value is set according to the rated value and maximum allowable voltage of the arm switches 33 and 36, and the capacitor upper limit value Vh is set according to this withstand voltage value.

As described above, in step S309, it is determined whether the motor rotation speed Nm is equal to or less than the rotation threshold value Nth. If the motor rotation speed Nm is not equal to or less than the rotation threshold value Nth, the process returns to step S301.

In step S302 from the second time onwards, the q-axis current command value Iq* is calculated by the voltage change unit 53 with the capacitor upper limit value Vh substituted for the capacitor command value Vc*. Specifically, the q-axis current command value Iq* is calculated so that the capacitor voltage Vc matches the capacitor upper limit value Vh. Note that the function of the control device 40 that executes the processing of step S302 from the second time onwards corresponds to the voltage increase unit. Also, the capacitor upper limit value Vh corresponds to the capacitor threshold value.

In step S301 from the second time onwards, the reactive power change unit calculates the d-axis current command value Id* with the capacitor upper limit value Vh substituted for the capacitor command value Vc*. Specifically, the d-axis current command value Id* is calculated so that the capacitor voltage Vc matches the capacitor upper limit value Vh and the motor rotation speed Nm matches the rotation threshold value Nth. In other words, the d-axis current command value Id* is calculated so that the capacitor voltage Vc increases and the motor rotation speed Nm decreases. Feedback control is used for this calculation. Note that the function of the control device 40 that executes the processing of step S301 from the second time onwards corresponds to the d-axis current command unit. The d-axis current command unit is sometimes called a reactive power control unit or a rotation reduction unit.

On the other hand, if the motor rotation speed Nm is equal to or lower than the rotation threshold value Nth, steps S310 to S317 are first performed. In step S317, it is determined whether the capacitor voltage Vc is equal to or lower than the battery voltage V0. Then, steps S310 to S317 are repeatedly performed until the capacitor voltage Vc becomes equal to or lower than the battery voltage V0.

After it is determined in step S309 that the motor rotation speed Nm is equal to or less than the rotation threshold value Nth, in steps S310 to S314 for the first time, the same processing as in steps S301 to S305 for the second time and thereafter is performed. For example, in step S310, the d-axis current command value Id* is set according to the capacitor voltage Vc and the motor rotation speed Nm, as in step S301 for the second time and thereafter. In step S311, the q-axis current command value Iq* is set according to the capacitor voltage Vc, as in step S302 for the second time and thereafter.

Steps S312 to S314 are two-phase control processes that perform two-phase control in the closing process. The two-phase control process in steps S312 to S314 is a process that is executed together with the voltage drop process described below. In steps S312 to S314, the inverter 30 is controlled so that the current phase difference PD2 is changed from 120 degrees to 60 degrees for two of the three phases excluding the abnormal phase. The function in the control device 40 that executes the processes in steps S312 to S314 corresponds to the opening control unit in the opening process.

In step S312, a two-phase voltage command is issued as in step S303. In step S313, switch driving is performed as in step S304. In step S314, abnormal phase off driving is performed as in step S305.

In steps S310 to S317, the capacitor mode has already been set in step S306. Step S316 and the second and subsequent steps S311 are voltage drop processing that performs voltage drop control in capacitor mode. Step S316 and the second and subsequent steps S310 are reactive power processing that performs reactive power control in capacitor mode.

In step S315, various information is acquired in the same manner as in step S307. However, in step S315, in addition to the capacitor voltage Vc and the motor rotation speed Nm, the battery voltage V0 is acquired using the detection signal of the battery voltage sensor 23. In step S316, the battery voltage V0 is substituted for the capacitor command value Vc*.

As described above, in step S317, it is determined whether the capacitor voltage Vc is equal to or lower than the battery voltage V0. If the capacitor voltage Vc is equal to or lower than the battery voltage V0, the process returns to step S310.

In step S311 from the second time onwards, the q-axis current command value Iq* is calculated by the voltage change unit 53 with the battery voltage V0 substituted for the capacitor command value Vc*. Specifically, the q-axis current command value Iq* is calculated so that the capacitor voltage Vc matches the battery voltage V0. Note that the function of the control device 40 that executes the process of step S311 from the second time onwards corresponds to the voltage drop unit.

In step S310 from the second time onwards, the reactive power change unit calculates the d-axis current command value Id* with the battery voltage V0 substituted for the capacitor command value Vc*. Specifically, the d-axis current command value Id* is calculated so that the capacitor voltage Vc matches the battery voltage V0 and the motor rotation speed Nm matches the rotation threshold value Nth. In other words, the d-axis current command value Id* is calculated so that the capacitor voltage Vc drops and the motor rotation speed Nm decreases. Note that the function of the control device 40 that executes the processing of step S310 from the second time onwards corresponds to the d-axis current command unit.

On the other hand, if the capacitor voltage Vc is the battery voltage V0, the process proceeds to step S318. In step S318, it is determined that both the motor rotation speed Nm and the capacitor voltage Vc have sufficiently decreased, and the switch 22 is transitioned from the open state to the closed state. Here, a close signal is output to the drive unit of the switch 22. This resumes the supply of power from the battery 11 to the power conversion device 13 and the motor 12. In step S319, the capacitor mode set in step S306 is released. Note that the function of the control device 40 that executes the process of step S318 corresponds to the closed transition unit. Also, the rotation threshold value Nth corresponds to the closed threshold value.

Next, the change in torque of the motor 12 when an inverter abnormality occurs will be described with reference to FIG. 15. Here, it is assumed that the inverter abnormality is an abnormality that allows the control device 40 to perform two-phase control.

Timing t1 in FIG. 15 is the timing when an inverter abnormality occurs. Before timing t1, normal three-phase control is performed by the control device 40, and the torque of the motor 12 is maintained at a value close to the torque command value. Just before timing t1 when the inverter abnormality occurs, the motor rotation speed Nm is equal to or lower than the rotation threshold value Nth. Therefore, two-phase control is started by the control device 40 with a closing process in response to the occurrence of the inverter abnormality. The switch 22 is in the closed state both before and after timing t1.

If the control device 40 performs two-phase control with the phase difference PD2 remaining at 120 degrees after an inverter abnormality occurs at timing t1, the torque of the motor 12 fluctuates significantly, straddling the torque command value. On the other hand, if the control device 40 changes the phase difference PD2 to 60 degrees and performs two-phase control after an inverter abnormality occurs at timing t1, the torque fluctuation is smaller than when the phase difference PD2 is 120 degrees. In this case, the torque of the motor 12 is generally smaller than the torque in three-phase control. However, as described above, since the motor rotation speed Nm is equal to or lower than the rotation threshold value Nth, positive torque is more likely to be generated in the motor 12.

Next, the change in motor speed Nm when an inverter abnormality occurs will be described with reference to FIG. 16. Here, as in FIG. 15, it is assumed that an inverter abnormality occurs in a manner that allows the control device 40 to perform two-phase control.

Timing t11 in FIG. 16 is the timing when an inverter abnormality occurs. Before timing t11, normal three-phase control is performed by the control device 40. Just before timing t11 when the inverter abnormality occurs, the motor rotation speed Nm is greater than the rotation threshold value Nth. In addition, the capacitor voltage Vc is approximately the same as the battery voltage V0. Therefore, when an inverter abnormality occurs, two-phase control is started by the control device 40 in the opening process, and the switch 22 transitions from the closed state to the open state. Also, when an inverter abnormality occurs, reactive power control is started together with two-phase control in the opening process.

After timing t11, voltage increase control is performed together with two-phase control during the opening process, causing the capacitor voltage Vc to rise toward the capacitor upper limit value Vh. In addition, after timing t11, the motor rotation speed Nm decreases. The decrease in motor rotation speed Nm occurs not only because the torque of the motor 12 decreases with the start of two-phase control, but also because reactive power control is being performed. When the motor rotation speed Nm is greater than the rotation threshold value Nth and the capacitor voltage Vc is less than the capacitor upper limit value Vh, negative torque is likely to occur in the motor 12.

After timing t11, at timing t12, the rising capacitor voltage Vc reaches the capacitor upper limit value Vh. Voltage increase control continues after timing t12, so that the capacitor voltage Vc is maintained at the capacitor upper limit value Vh. Meanwhile, reactive power control continues after timing t12, so that the motor rotation speed Nm continues to decrease toward the rotation threshold value Nth. When the capacitor voltage Vc is at the capacitor upper limit value Vh, the motor rotation speed Nm becomes smaller to a certain extent, so that the motor 12 tends to become zero torque.

After timing t12, at timing t13, the motor rotation speed Nm, which had been decreasing, reaches the rotation threshold value Nth. After timing t13, as the motor rotation speed Nm decreases to the rotation threshold value Nth, voltage decrease control is performed instead of voltage increase control in the opening process. As a result, the capacitor voltage Vc decreases toward the capacitor upper limit value Vh. Meanwhile, reactive power control is continued even after timing t13, so that the motor rotation speed Nm is maintained at the rotation threshold value Nth. When the motor rotation speed Nm is at the rotation threshold value Nth, it becomes easier for positive torque to be generated in the motor 12.

After timing t13, at timing t14, the capacitor voltage Vc, which had been decreasing, reaches the battery voltage V0. Accordingly, the switch 22 is shifted from the open state to the closed state. After timing t14, the capacitor voltage Vc decreases to the battery voltage V0, and two-phase control is performed with the closing process.

If the motor rotation speed Nm becomes greater than the rotation threshold value Nth again after timing t14, the control device 40 switches the switch 22 to the open state again. Then, the control device 40 starts two-phase control in the opening process again. One example of a case in which the motor rotation speed Nm becomes greater than the rotation threshold value Nth again is when the vehicle is traveling downhill.

<Constituent Group A>
According to the present embodiment described so far, when an abnormality occurs in the one-phase conversion circuit 31 and the motor 12 is driven by the remaining two-phase conversion circuits 31, the current phase difference PD2 is changed from 120 degrees to 60 degrees in the two-phase control in the closing process. By changing the phase difference PD2 from 120 degrees to 60 degrees, the shape of the rotating magnetic field MFR of the motor 12 can be made closer to a circle. In this case, the magnitude of the composite magnetic field MFS is less likely to vary depending on the phase, and the back electromotive force of the motor 12 is less likely to vary depending on the phase. Therefore, it is less likely that the back electromotive force of the motor 12 becomes excessively large at a specific phase, causing an overcurrent to flow in the inverter 30, which in turn causes the inverter 30 to heat up. Therefore, the generation of heat due to the occurrence of an abnormality in the inverter 30 can be suppressed.

In the drive system 10, bringing the shape of the rotating magnetic field MFR closer to a circle improves the behavior of the rotating magnetic field MFR. Therefore, by changing the phase difference PD2 in two-phase control, the behavior of the rotating magnetic field MFR can be improved. Also, in the drive system 10, preventing the back electromotive force of the motor 12 from varying depending on the phase results in proper management of the back electromotive force of the motor 12. Therefore, by improving the behavior of the rotating magnetic field MFR, the back electromotive force of the motor 12 can be properly managed.

Unlike this embodiment, for example, a configuration is assumed in which the phase difference PD2 in two-phase control is naturally maintained at 120 degrees when an abnormality occurs in the one-phase conversion circuit 31. In this configuration, the rotating magnetic field MFR generated by the two-phase control becomes elliptical, the magnitude of the composite magnetic field MFS varies depending on the phase, and the back electromotive force of the motor 12 also varies depending on the phase. For example, if the back electromotive force becomes excessively large at a specific phase, there is a concern that an overcurrent will flow through the inverter 30 at this phase, causing the inverter 30 to heat up.

In the drive system 10, the back electromotive force of the motor 12 varies depending on the phase, making it difficult to properly manage the back electromotive force of the motor 12. Furthermore, the rotating magnetic field MFR becoming elliptical is an unsuitable form for managing the back electromotive force of the motor 12.

Furthermore, in a configuration in which the phase difference PD2 is kept at 120 degrees as described above, there is concern that the magnitude of the composite magnetic field MFS varies depending on the phase, which may result in increased torque ripple and decreased controllability of the control device 40 over the motor 12. In contrast, according to this embodiment, as described above, the phase difference PD2 is changed so that the magnitude of the composite magnetic field MFS is less likely to vary depending on the phase. This makes it possible to suppress torque ripple and deterioration of controllability. In this way, by suppressing torque ripple and deterioration of controllability, drivability can be improved.

When ASC is performed by the evacuation process rather than the two-phase control in response to the occurrence of an inverter abnormality, the current between the motor 12 and the smoothing capacitor 21 is cut off. Therefore, the back electromotive force of the motor 12 is restricted from being supplied to the smoothing capacitor 21. However, the current due to the back electromotive force of the motor 12 flows through the arm switch 33, 36 that has received the ON command among the upper arm group 38a, 39a and the lower arm group 38b, 39b. Here, when the motor 12 is increased in output, the interlinkage magnetic flux, which is the field magnetic flux generated in the motor 12, increases. Therefore, in a state where ASC is performed, the current flowing through the arm switches 33, 36 that are in the ON state increases in proportion to the interlinkage magnetic flux. Therefore, there is a concern that the heat generated in the inverter 30 due to the current flowing through the arm switches 33, 36 will become excessively large. As a result, the cooling of the inverter 30 will not be able to keep up with the heat generation, resulting in a "heat failure state."

In contrast, according to the present embodiment, as described above, the phase difference PD2 is changed to 60 degrees and two-phase control is performed. This prevents the current flowing through the arm switches 33 and 36 in the on state from increasing excessively. This prevents the inverter 30 from entering a "non-thermal state."

In this embodiment, the conversion circuit 31 in the inverter 30 is an H-bridge circuit. That is, in the inverter 30, the first inverter section 38 is connected to one end of the winding 12a, and the second inverter section 39 is connected to the other end of the winding 12a. In this configuration, the U-phase current Iu, the V-phase current Iv, and the W-phase current Iw can each be individually controlled by the control device 40. Therefore, if an abnormality occurs in one of the conversion circuits 31, the control device 40 can drive the motor 12 by performing two-phase control on the remaining two-phase conversion circuits 31.

Unlike this embodiment, for example, a configuration is assumed in which a conversion circuit that is not an H-bridge circuit is connected to only one end of the winding 12a, and a Y connection is formed by the other end of the winding 12a. In this configuration, there is a constraint that the sum of the three-phase currents is zero, and it is difficult to individually control the U-phase current Iu, the V-phase current Iv, and the W-phase current Iw by the control device 40. For this reason, if an abnormality occurs in one of the conversion circuits in the inverter 30, even if the control device 40 controls the conversion circuits of the remaining two phases to drive the motor 12, torque ripple and controllability will deteriorate, making it difficult to drive the motor 12 properly.

According to this embodiment, for an abnormal phase of the inverter 30, all arm switches 33, 36 except for the abnormal switch are driven to be off in the conversion circuit 31. This realizes a configuration in which current to the winding 12a connected to the conversion circuit 31 is cut off for an abnormal phase of the inverter 30. With this configuration, it is less likely that current will flow through the conversion circuit 31 or the winding 12a. In this way, when the control device 40 performs two-phase control, it is less likely that unintended current will flow through the abnormal phase of the inverter 30, so that the control accuracy of the motor 12 by two-phase control can be improved.

According to this embodiment, when the phase difference PD2 is changed from 120 degrees to 60 degrees in two-phase control, the rotating magnetic field MFR becomes circular. With this configuration, the resultant magnetic field MFS is less likely to vary depending on the phase. This makes it possible to suppress the back electromotive force of the motor 12 from varying depending on the phase, as well as the deterioration of torque ripple and controllability.

According to this embodiment, in the control device 40, the voltage command values Vu*, Vv*, and Vw* are set so that the phase difference PD2 is 60 degrees in two-phase control. Therefore, if an abnormality occurs in the conversion circuit 31 of one phase, it is possible for the conversion circuits 31 of the remaining two phases to set the current phase difference PD2 to 60 degrees.

According to this embodiment, when setting the voltage command values Vu*, Vv*, and Vw*, the two-phase to three-phase conversion unit 46 uses formulas 1 to 3 and formulas 4 to 6 for three-phase control and two-phase control. In this case, the phase difference PD2 can be changed in two-phase control by simply using the calculation formulas for three-phase control and two-phase control, so the calculation load can be reduced. Unlike this embodiment, for example, in a configuration in which the two-phase to three-phase conversion unit 46 has separate function blocks for setting the voltage command values Vu*, Vv*, and Vw* for three-phase control and two-phase control, a storage capacity is required to construct these function blocks. In contrast, according to this embodiment, it is sufficient to use the calculation formulas for two-phase control and three-phase control, and there is no need to provide a function block for calculation. Therefore, the storage capacity of the control device 40 can be reduced for the calculation of the voltage command values Vu*, Vv*, and Vw*.

According to this embodiment, two-phase control in the closed process is performed when the motor rotation speed Nm is not greater than the rotation threshold value Nth. Therefore, in the two-phase control in the closed process, it is possible to avoid a situation in which the magnitude of the rotating magnetic field MFR is insufficient to drive the motor 12, causing a back electromotive force of the motor 12 to be generated and an overcurrent to flow in the inverter 30.

<Composition group B>
According to this embodiment, when an abnormality occurs in the one-phase conversion circuit 31 and the motor 12 is driven by the remaining two-phase conversion circuit 31, the q-axis current command value Iq* is set by the voltage increase process so that the capacitor voltage Vc increases beyond the battery voltage V0. Moreover, in this case, since the switch 22 has already been shifted to the open state, the capacitor voltage Vc is likely to increase beyond the battery voltage V0. Then, the capacitor voltage Vc that is greater than the battery voltage V0 is used to drive the motor 12 via the inverter 30, thereby improving the state of the rotating magnetic field MFR. This makes it easier to manage the back electromotive force of the motor 12. If the back electromotive force of the motor 12 can be appropriately managed, it becomes difficult for an overcurrent to flow through the inverter 30 due to the back electromotive force of the motor 12, causing the inverter 30 to generate heat. Therefore, heat generation due to the occurrence of an abnormality in the inverter 30 can be suppressed.

In a situation where the battery voltage V0 is used by the inverter 30 to drive the motor 12, the motor rotation speed Nm at which a positive torque is generated in the motor 12 when two-phase control is being performed is a smaller rotation speed than when three-phase control is being performed. In other words, the maximum rotation speed of the motor 12 that can be driven by two-phase control is smaller than the maximum rotation speed of the motor 12 that can be driven by three-phase control. For this reason, when the motor rotation speed Nm is in the high rotation range, the motor 12 cannot be driven by two-phase control, and the motor 12 is more likely to generate a back electromotive force.

In contrast, according to this embodiment, when the motor rotation speed Nm is greater than the rotation threshold value Nth, the switch 22 is switched to the open state and the voltage increase process is performed. This makes it possible to avoid a situation in which the motor rotation speed Nm is greater than the rotation threshold value Nth, resulting in a shortage of voltage used to drive the motor 12 and the generation of negative torque in the motor 12. In other words, it is possible to avoid a situation in which the process of switching the switch 22 to the open state and the process of increasing the capacitor voltage Vc beyond the battery voltage V0 are not performed even though the motor rotation speed Nm is in a high rotation range greater than the rotation threshold value Nth. This makes it possible to suppress the generation of counter electromotive force in the motor 12 due to the motor rotation speed Nm being greater than the rotation threshold value Nth.

According to this embodiment, the rotation threshold value Nth is the rotation speed at which the motor 12 can be driven by two-phase control in the closed process. In other words, the rotation threshold value Nth is the rotation speed at which the motor 12 does not generate negative torque when the switch 22 is in the closed state. This makes it possible to avoid a situation in which the process of switching the switch 22 to the open state and the voltage increase process targeting the capacitor voltage Vc are not performed even if the motor rotation speed Nm is so large that the motor 12 cannot be driven by two-phase control at the battery voltage V0. This makes it possible to suppress the generation of back electromotive force in the motor 12 due to the battery voltage V0 being insufficient to drive the motor 12 by two-phase control.

According to this embodiment, in the voltage increase process in the open process, the q-axis current command value Iq* is set so that the capacitor voltage Vc increases to the capacitor upper limit value Vh. Then, in the control device 40, vector control is performed so that the q-axis current Iq coincides with the q-axis current command value Iq*. Therefore, the capacitor voltage Vc can be increased more reliably to the capacitor upper limit value Vh.

According to this embodiment, the capacitor upper limit value Vh is the inverter upper limit value, which is the upper limit value of the voltage applied to the inverter 30. Therefore, it is possible to prevent the capacitor voltage Vc from rising above the battery voltage V0, which would cause an overvoltage to the inverter 30. Therefore, it is possible to suppress both the occurrence of an overcurrent in the inverter 30 due to the back electromotive force of the motor 12, and the occurrence of an overvoltage to the inverter 30 due to the capacitor voltage Vc. In addition, by preventing the capacitor voltage Vc from becoming a value greater than the inverter upper limit value, the current required for reactive power control is reduced. Therefore, it is possible to reduce losses in the inverter 30 and losses in the motor 12 caused by reactive power control.

According to this embodiment, in the reactive power processing in the open process, the d-axis current command value Id* is set so that the motor rotation speed Nm is reduced. Therefore, if an abnormality occurs in the one-phase conversion circuit 31 and the motor rotation speed Nm is greater than the rotation threshold value Nth, the motor rotation speed Nm can be actively reduced by reactive power control. In this case, the time required for the motor rotation speed Nm to decrease and reach the rotation threshold value Nth can be shortened.

According to this embodiment, in the reactive power processing in the open process, the d-axis current command value Id* is set according to the capacitor voltage Vc. Therefore, when an abnormality occurs in the one-phase conversion circuit 31, the capacitor voltage Vc can be actively both increased and decreased by reactive power control. For example, when the capacitor voltage Vc is increased, the time required for the capacitor voltage Vc to reach the capacitor upper limit value Vh can be shortened. Also, when the capacitor voltage Vc is decreased, the time required for the capacitor voltage Vc to reach the battery voltage V0 can be shortened.

According to this embodiment, when the motor rotation speed Nm decreases to the rotation threshold value Nth during the opening process, the switch 22 transitions to the closed state and the opening process ends. This makes it possible to avoid a situation in which the switch 22 does not transition to the closed state and the motor 12 cannot be driven by power from the battery 11 even though the motor rotation speed Nm has decreased to a level where the motor 12 can be properly driven by the battery voltage V0.

When the opening process ends, if the capacitor voltage Vc and the battery voltage sensor 23 are different, a circulating current is likely to occur that circulates between the battery 11 and the smoothing capacitor 21. In contrast, according to this embodiment, the switch 22 is transitioned to a closed state on the condition that the capacitor voltage Vc has decreased to the battery voltage V0. This makes it possible to suppress the occurrence of a circulating current that flows between the battery 11 and the smoothing capacitor 21.

According to this embodiment, in the two-phase control in the open process, the current phase difference PD2 is changed from 120 degrees to 60 degrees. This allows the shape of the rotating magnetic field MFR of the motor 12 to approach a circle, similar to the two-phase control in the close process. Therefore, in the open process, in addition to the process of decreasing the motor rotation speed Nm, the process of increasing the capacitor voltage Vc, and the process of decreasing the capacitor voltage Vc, two-phase control can be performed to suppress heat generation due to the occurrence of an abnormality in the inverter 30.

Second Embodiment
In the first embodiment, the arm switches 33, 36 and the winding 12a are directly connected, but in the second embodiment, at least one of the arm switches 33, 36 and the winding 12a is connected via a winding switch 59. The configurations, actions, and effects not specifically described in this embodiment are the same as those in the first embodiment. In this embodiment, the differences from the first embodiment will be mainly described.

As shown in FIG. 17, the power conversion device 13 has a winding switch 59. The winding switch 59 electrically connects the arm switch 36 of the second arm circuit 35 and the winding 12a in each of the conversion circuits 31 of the U-phase, V-phase, and W-phase. The arm switch 36 of the second arm circuit 35 and the winding 12a are connected via the winding switch 59. On the other hand, the arm switch 33 of the first arm circuit 32 and the winding 12a are directly connected without going through the winding switch 59.

The winding switch 59 is formed of a switching element such as a semiconductor element. The winding switch 59 is formed of a switch or relay that can be switched between an open state and a closed state, and is provided on the output line 27b. In each of the conversion circuits 31 for the U, V, and W phases, when the winding switch 59 is in the closed state, current can flow between the arm circuits 32, 35 and the winding 12a. On the other hand, when the winding switch 59 is in the open state, current is cut off between the arm circuits 32, 35 and the winding 12a.

The winding switch 59 may electrically connect the arm switch 33 of the first arm circuit 32 to the winding 12a in each of the conversion circuits 31 of the U-phase, V-phase, and W-phase. The winding switch 59 only needs to connect at least one of the arm switches 33 and 36 to the winding 12a. In this configuration, the winding switch 59 is provided on the output line 27a.

The winding switch 59 is provided with a drive unit that drives the winding switch 59 to open and close. The winding switch 59 is electrically connected to the control device 40. The control device 40 controls the drive of the drive unit to cause the winding switch 59 to open and close. The control device 40 is capable of opening and closing the winding switch 59 for each of the U-phase, V-phase, and W-phase individually.

The control device 40 controls the drive of the winding switch 59 during the closing process of the inverter control process. Here, the closing process of this embodiment will be explained with reference to the flowchart in FIG. 18.

In FIG. 18, steps S201 to S205 are the same as those in the first embodiment. After step S205, in step S401, current is cut off. Here, the winding switch 59 is opened for the abnormal phase of the inverter 30. If the winding switch 59 for the abnormal phase of the inverter 30 is closed, the winding switch 59 transitions from the closed state to the open state. On the other hand, if the winding switch 59 is already open, the winding switch 59 is maintained in the open state. In either case, current is cut off to the winding 12a for the abnormal phase of the inverter 30. The functions of the control device 40 that execute the process of S401 correspond to the phase change unit, the cutoff execution unit, and the winding opening unit.

In the closing process, the winding switch 59 cuts off the power supply to the winding 12a for the abnormal phase of the inverter 30, and steps S203 to S205 are performed for the second and subsequent times as two-phase control. Note that if the power supply is cut off in step S401, the abnormal phase off drive in step S205 does not need to be performed. This is because the power supply to the winding 12a is cut off by the winding switch 59 for the abnormal phase even if the conversion circuit 31 does not turn off all arm switches 33, 36 except for the abnormal switch.

The control device 40 controls the drive of the winding switch 59 in the opening process, similar to the closing process. Here, the opening process of this embodiment will be described with reference to the flowchart in FIG. 19.

In FIG. 19, in steps S301 to S305, the same processing as in the first embodiment is performed. After step S305, in step S501, current is cut off. In steps S306 to S314, the same processing as in the first embodiment is performed, and after step S314, in step S502, current is cut off. In both steps S501 and S502, the winding switch 59 is opened for the abnormal phase of the inverter 30, similar to step S401 in the closing process. The functions of the control device 40 that execute the processing of S501 and S502 correspond to the phase change unit, the cutoff execution unit, and the winding opening unit.

In the opening process, the winding switch 59 cuts off the power supply to the winding 12a for the abnormal phase of the inverter 30, and steps S303 to S305 and S312 to S314 are performed for the second and subsequent times as two-phase control. Note that if power supply is cut off in steps S501 and S502, it is not necessary to perform the abnormal phase off drive in steps S305 and S314. This is because, as with the closing process, the winding switch 59 cuts off the power supply to the winding 12a for the abnormal phase even if the conversion circuit 31 does not turn off all arm switches 33 and 36 except for the abnormal switch.

According to this embodiment, in both the closing process and the opening process, the winding switch 59 cuts off the current flow to the winding 12a by the conversion circuit 31 of the abnormal phase. Therefore, even if the type of inverter abnormality is a short circuit abnormality of the arm switches 33, 36, the winding switch 59 can reliably prevent current from flowing unintentionally to the winding 12a through the abnormality switch. Therefore, when two-phase control is being performed following the occurrence of an inverter abnormality, it is possible to prevent control failure caused by unintentional current flowing to the winding 12a for the abnormal phase.

When an inverter abnormality occurs, even if all arm switches 33, 36 for the abnormal phase are in the off state, there is a concern that a circulating current will flow through the winding 12a via the diodes 34, 37. In this case, even if the phase difference PD2 is changed from 120 degrees to 60 degrees in two-phase control, a circulating current will flow through the abnormal phase, making it difficult for the rotating magnetic field MFR of the motor 12 to become circular. In other words, the magnitude of the composite magnetic field MFS generated by two-phase control is likely to vary depending on the phase.

In contrast, according to the present embodiment, the winding switch 59 is switched to the open state for the abnormal phase, and the circulating current flowing through the diodes 34, 37 and the winding 12a is cut off. This prevents the rotating magnetic field MFR of the motor 12 from becoming circular due to the circulating current flowing for the abnormal phase. In other words, it prevents the magnitude of the composite magnetic field MFS generated by the two-phase control from varying depending on the phase.

In this embodiment, the arm switches 33, 36 are formed by switching elements in which open circuit abnormalities are more likely to occur than short circuit abnormalities. In this way, in the power conversion device 13 in which short circuit abnormalities are more likely to occur as inverter abnormalities than open circuit abnormalities, it is preferable to forcibly cut off the current to the winding 12a for the abnormal phase by the winding switch 59 in order to suppress control failure in two-phase control.

In this embodiment, in step S103 of the inverter control process shown in FIG. 11, the determination of whether or not two-phase control is to be performed may be made by determining whether or not each of the first arm circuit 32 and the second arm circuit 35 includes one abnormal switch. For example, if each of the arm circuits 32 and 35 includes one abnormal switch for the abnormal phase, two-phase control is performed, and the process proceeds to step S104, where the opening process of step S107 and the closing process of step S109 are performed. Even if each of the arm circuits 32 and 35 includes one abnormal switch, as described above, the winding switch 59 is opened in the opening process and closing process, thereby preventing current from unintentionally flowing through the winding 12a through these abnormal switches.

Third Embodiment
In the first embodiment, the voltage changing unit 53 sets the q-axis current command value Iq* in accordance with the capacitor voltage Vc. In contrast, in the third embodiment, the voltage changing unit 53 sets the q-axis current command value Iq* in accordance with the state of the motor 12. The configurations, actions, and effects not specifically described in this embodiment are similar to those of the first embodiment. In this embodiment, the differences from the first embodiment will be mainly described.

20, the control device 40 has a motor temperature acquisition unit 61 as a functional block. The motor temperature acquisition unit 61 acquires the motor temperature Tm, which is the temperature of the motor 12, as a detection value using signals input from a higher-level ECU or various sensors. For example, a temperature sensor such as a thermistor for detecting temperature is provided around the motor 12, and the motor temperature acquisition unit 61 calculates and acquires the motor temperature Tm using a detection signal from this temperature sensor. The motor temperature acquisition unit 61 may estimate and acquire the motor temperature Tm using the phase currents Iu, Iv, Iw and the phase voltages Vu, Vv, Vw, etc., as detection values. The motor temperature acquisition unit 61 may also estimate and acquire the motor temperature Tm using the d-axis current Id, the q-axis current Iq, the d-axis voltage Vd, the q-axis voltage Vq, etc.

As in the first embodiment, the voltage change unit 53 is a functional block for setting the q-axis current command value Iq* in steps S302 and S311 from the second time onwards in the opening process shown in FIG. 13.

The voltage change unit 53 sets the q-axis current command value Iq* according to the motor rotation speed Nm and the motor temperature Tm. The motor rotation speed Nm and the motor temperature Tm are motor information indicating the state of the motor 12. The motor temperature Tm acquired by the motor temperature acquisition unit 61 is input to the voltage change unit 53. In addition to the motor temperature Tm, the motor rotation speed Nm is input to the voltage change unit 53. This motor rotation speed Nm is a value acquired in steps S307 and S315 in the opening process shown in FIG. 13. The voltage change unit 53 performs feedforward control using the correlation map 63 to set the q-axis current command value Iq* from the motor rotation speed Nm and the motor temperature Tm.

The correlation map 63 is correlation information showing the correlation between the motor rotation speed Nm, the motor temperature Tm, the q-axis current Iq, and the capacitor voltage Vc. The correlation map 63 is information obtained by testing, simulation, etc., and is stored in the memory unit of the control device 40. Note that the correlation map 63 includes correlations between at least the motor rotation speed Nm, the motor temperature Tm, and the q-axis current Iq as parameters. In other words, the parameters of the correlation map 63 do not necessarily need to include the capacitor voltage Vc. The correlation map 63 is sometimes referred to as correlation information.

The correlation map 63 may be a map including information on the q-axis current Iq that is likely to generate a back electromotive force of the motor 12 with respect to the motor rotation speed Nm and the motor temperature Tm, or a map including information on the q-axis current Iq that is likely not to generate a back electromotive force of the motor 12. In the opening process shown in FIG. 13, different maps are used as the correlation map 63 in steps S302 and S311. For example, the correlation map 63 used in step S302 includes information on the q-axis current Iq for increasing the capacitor voltage Vc. Therefore, the voltage increase process including step S302 is executed, and the capacitor voltage Vc increases toward the capacitor upper limit value Vh. On the other hand, the correlation map 63 used in step S311 includes information on the q-axis current Iq for decreasing the capacitor voltage Vc. Therefore, the voltage decrease process including step S311 is executed, and the capacitor voltage Vc decreases toward the battery voltage V0.

According to this embodiment, the voltage change unit 53 sets the q-axis current command value Iq* using the correlation map 63, so there is no need to perform feedback control. This makes it possible to improve the responsiveness of the process for setting the q-axis current command value Iq* in the voltage increase process and voltage decrease process of the opening process. This makes it possible to improve the responsiveness of the control device 40 to increases and decreases in the capacitor voltage Vc and changes in the motor rotation speed Nm when managing the capacitor voltage Vc.

According to this embodiment, the q-axis current command value Iq* is set according to the motor rotation speed Nm and the motor temperature Tm. Therefore, the back electromotive force of the motor 12 can be appropriately managed by utilizing the fact that the back electromotive force of the motor 12 changes according to both the motor rotation speed Nm and the motor temperature Tm.

Fourth Embodiment
In the first embodiment, the voltage change unit 53 sets the q-axis current command value Iq* by feedback control. In the third embodiment, the voltage change unit 53 sets the q-axis current command value Iq* by feedforward control. In contrast, in the fourth embodiment, the voltage change unit 53 sets the q-axis current command value Iq* by both feedback control and feedforward control. The configurations, actions, and effects not specifically described in this embodiment are the same as those in the second embodiment. In this embodiment, the differences from the first and third embodiments will be mainly described.

As shown in FIG. 21, in the voltage change unit 53, the capacitor control unit 55 sets the q-axis current command value Iq* by feedback control, as in the first embodiment. The q-axis current command value Iq* set in this manner by feedback control is referred to as the first command value. Also, in the voltage change unit 53, the correlation map 63 is used to set the q-axis current command value Iq* by feedforward control, as in the third embodiment. The q-axis current command value Iq* set in this manner by feedforward control is referred to as the second command value.

The voltage change unit 53 has a general setting unit 65. The general setting unit 65 receives a first command value set by feedback control and a second command value set by feedforward control. The general setting unit 65 sets the q-axis current command value Iq* using both the first command value and the second command value. The q-axis current command value Iq* set by the general setting unit 65 is a general command value set comprehensively from the first command value and the second command value, and is input to the d-axis subtraction unit 43.

The overall setting unit 65, for example, calculates the average value of the first command value and the second command value, and sets this average value as the q-axis current command value Iq*. The overall setting unit 65 may preferentially use one of the first command value and the second command value to set the q-axis current command value Iq*. For example, the overall setting unit 65 determines whether to prioritize management accuracy or responsiveness for the capacitor voltage Vc, and when it is determined that management accuracy is to be prioritized, it sets the first command value calculated by feedback control as the q-axis current command value Iq* as is. On the other hand, when it is determined that responsiveness is to be prioritized, the overall setting unit 65 sets the second command value calculated by feedforward control as the q-axis current command value Iq* as is.

<Other embodiments>
The disclosure of this specification is not limited to the exemplified embodiments. The disclosure includes the exemplified embodiments and modifications made by those skilled in the art based thereon. For example, the disclosure is not limited to the combination of parts and elements shown in the embodiments, and can be implemented in various modifications. The disclosure can be implemented by various combinations. The disclosure can have additional parts that can be added to the embodiments. The disclosure includes those in which parts and elements of the embodiments are omitted. The disclosure includes the replacement or combination of parts and elements between one embodiment and another embodiment. The disclosed technical scope is not limited to the description of the embodiments. The disclosed technical scope is indicated by the description of the claims, and should be interpreted as including all modifications within the meaning and scope equivalent to the description of the claims.

<Constituent Group A>
In each of the above embodiments, the change value by which the phase difference is changed in abnormality control such as two-phase control does not have to be 60 degrees. The change value of the phase difference may be a value that makes the rotating magnetic field MFR of the motor 12 closer to a circle than when the phase difference PD2 is kept at 120 degrees. For example, in two-phase control, examples of change values that make the rotating magnetic field MFR closer to a circle than when the phase difference PD2 is 120 degrees include 30 degrees and 90 degrees. For example, as shown in FIG. 7, when the phase difference PD2 is set to 30 degrees, the rotating magnetic field MFR becomes closer to a circle than when the phase difference PD2 is 120 degrees. Also, as shown in FIG. 8, when the phase difference PD2 is set to 90 degrees, the rotating magnetic field MFR becomes closer to a circle than when the phase difference PD2 is 120 degrees. When the phase difference PD2 is changed to 30 degrees or 90 degrees, βu, βv, and βw in Equations 4 to 6 may be set so that the phase difference PD2 becomes 30 degrees or 90 degrees. The phase difference PD2 at which the rotating magnetic field MFR becomes circular can be, in addition to 60 degrees, a value slightly greater or less than 60 degrees.

In each of the above embodiments, in abnormality control such as two-phase control, the phases changed for at least two phases of current do not have to be the same value. For example, in the case of two-phase control, when changing the phase difference PD2 from 120 degrees to 60 degrees, the phases changed for the two phases of current do not have to be 30 degrees each. For example, the phase changed for one of the two phases of current may be 60 degrees, and the phase for the other phase may not be changed.

In each of the above embodiments, when setting the voltage command values Vu*, Vv*, and Vw*, a common calculation formula may be used for three-phase control and two-phase control. For example, a configuration may be adopted in which formulas 4 to 6 are used in both three-phase control and two-phase control. When formulas 4 to 6 are used in three-phase control, zero is substituted for βu, βv, and βw to calculate the voltage command values Vu*, Vv*, and Vw*. In two-phase control, the voltage command values Vu*, Vv*, and Vw* are calculated using formulas 4 to 6, as in the first embodiment.

In each of the above embodiments, the two-phase to three-phase conversion unit 46 may have separate functional blocks for calculating the voltage command values Vu*, Vv*, and Vw*, one for use in three-phase control and one for use in two-phase control. The two-phase to three-phase conversion unit 46 may also calculate the voltage command values Vu*, Vv*, and Vw* using correlation information or functions such as maps instead of or in addition to the calculation formulas such as Equations 1 to 6.

In each of the above embodiments, in abnormality control such as two-phase control, it is not necessary to calculate the voltage command value for the abnormal phase among the voltage command values Vu*, Vv*, and Vw*. For example, zero may be substituted for the voltage command value for the abnormal phase. Also, for the abnormal phase, it is not necessary to generate a drive command after calculating the voltage command value. For example, a signal that is always zero may be used as the drive command.

In each of the above embodiments, two-phase control may be performed in the closing process regardless of the motor rotation speed Nm. For example, two-phase control may be performed in the closing process both when the motor rotation speed Nm is greater than the rotation threshold value Nth and when it is not greater than the rotation threshold value Nth. In other words, the opening process may not be performed.

In each of the above embodiments, in the two-phase control of the closing process, the command torque used to set the current command values Id* and Iq* may be changed. For example, the current command unit 41 determines whether the maximum value of the torque generated by driving the motor 12 by the battery voltage V0 is smaller than the command torque. If the maximum value is smaller than the command torque, the command torque is changed by substituting the maximum value for the command torque. This makes it possible to eliminate the situation in which the torque generated by the motor 12 cannot reach the command torque in the two-phase control of the closing process.

In each of the above embodiments, the motor 12 may be a four or more phase AC motor as long as it is a multi-phase AC motor. When the motor 12 is a four or more phase AC motor, the power conversion device 13 is provided with an inverter 30 of four or more phases. In this inverter 30, a conversion circuit 31 corresponding to each of the four or more phases is provided. In the inverter control process, when an abnormality occurs in one or more conversion circuits 31, if two or more conversion circuits 31 remain that are not abnormal, abnormality control may be performed on these two or more conversion circuits 31. For example, in the power conversion device 13 that drives a four-phase motor, when an abnormality occurs in one conversion circuit 31, three-phase control is performed on the remaining three conversion circuits 31.

In abnormality control targeting a conversion circuit of two or more phases, the phase differences of the remaining two or more phases of current are changed so that the rotating magnetic field MFR of the motor 12 becomes closer to a circle than when the phase differences of the remaining two or more phases of current are at natural values. For example, in a drive system in which the motor 12 and the inverter 30 are each four-phase, if an abnormality occurs in the conversion circuit 31 of one phase, abnormality control is assumed to be performed by the conversion circuit 31 of the remaining three phases. In this abnormality control, the phase differences of the remaining three phases of current are changed so that the rotating magnetic field MFR of the motor 12 becomes closer to a circle than when the phase differences of the remaining three phases of current are at natural values.

<Composition group B>
In each of the above embodiments, in the voltage increase process of the opening process, the q-axis current command value Iq* may be set so that the capacitor voltage Vc increases beyond the battery voltage V0. For example, the capacitor upper limit value Vh may be set regardless of the maximum allowable voltage or the rated voltage of the smoothing capacitor 21. Also, the q-axis current command value Iq* may be set so that the capacitor voltage Vc coincides with a predetermined voltage value. Similarly, in the reactive power process of the opening process, the d-axis current command value Id* may be set so that the capacitor voltage Vc increases beyond the battery voltage V0.

In each of the above embodiments, the rotation threshold value Nth, which is the criterion for determining whether or not to perform the opening process, may be a predetermined value regardless of the torque generated by the motor 12. In addition, the rotation threshold value Nth may be set according to the capacitor voltage Vc, the motor temperature Tm, etc.

In each of the above embodiments, the torque of the motor 12, the capacitor voltage Vc, the motor temperature Tm, etc. may be used as a parameter for determining whether or not to perform the opening process, instead of the motor rotation speed Nm. For example, it is determined whether the maximum value of the torque generated by driving the motor 12 with the battery voltage V0 is smaller than the command torque. If the maximum value is smaller than the command torque, the opening process is performed instead of the closing process.

In each of the above embodiments, in the two-phase control of the opening process, the process of changing the phase difference PD2 may not be performed. For example, in steps S303 and S312 of the opening process, a two-phase voltage command may be performed so that the phase difference PD2 remains at 120 degrees as it is. For example, Equations 1 to 3 may be used to set the voltage command values Vu*, Vv*, and Vw*, as in the three-phase control.

In each of the above embodiments, among the processes of steps S301 and S310 for setting the d-axis current command value Id*, not only the second and subsequent processes but all processes may be performed as opening processes corresponding to the d-axis current command unit. For example, for step S301, the same processes as steps S306 to S308 may be performed at a stage prior to step S301. In this step S301, as with the second and subsequent processes, the d-axis current command value Id* is calculated in the first process so that the capacitor voltage Vc matches the capacitor upper limit value Vh.

Of the processes in step S302 for setting the q-axis current command value Iq*, opening processes may be performed so that not only the second and subsequent processes, but all processes correspond to the voltage rise section. For example, the same processes as steps S306 to S308 may be performed at a stage prior to step S302. In this step S302, as in the second and subsequent processes, the q-axis current command value Iq* is calculated in the first process so that the capacitor voltage Vc matches the capacitor upper limit value Vh.

Of the processes in step S311 for setting the q-axis current command value Iq*, opening processes may be performed so that not only the second and subsequent processes, but all processes correspond to the voltage drop section. For example, the same processes as steps S315 and S316 may be performed at a stage prior to step S311. In this step S311, as in the second and subsequent processes, the q-axis current command value Iq* is calculated in the first process so that the capacitor voltage Vc matches the battery voltage V0.

In each of the above embodiments, the capacitor upper limit value Vh may be set according to the withstand voltage of the inverter 30 and the withstand voltage value of the drive system 10. For the drive system 10, the upper limit value of the voltage applied to the drive system 10 is set as the withstand voltage value according to the respective rated values and maximum allowable voltages. The withstand voltage value of the component or device with the lowest withstand voltage in the drive system 10 is set as the withstand voltage value of the drive system 10.

In each of the above embodiments, in the opening process, the d-axis current command value Id* may be set according to the command torque, regardless of either the motor rotation speed Nm or the capacitor voltage Vc. Also, in the opening process, the d-axis current command value Id* may be set according to only the motor rotation speed Nm out of the motor rotation speed Nm and the capacitor voltage Vc. For example, in steps S301 and S310 of the opening process, the d-axis current command value Id* may be set so that the motor rotation speed Nm coincides with the rotation threshold value Nth, regardless of the capacitor voltage Vc.

In each of the above embodiments, the opening threshold and closing threshold, which are the criteria for opening and closing the switch 22, may be different values rather than being the rotation threshold Nth. For example, the opening threshold may be set to a value greater than the closing threshold. In this configuration, the motor rotation speed Nm when the opening process is terminated and the closing process is started is smaller than the motor rotation speed Nm when the opening process is started due to the occurrence of an inverter abnormality. Therefore, it is possible to reliably prevent the generation of a back electromotive force in the motor 12 due to the motor rotation speed Nm being large.

In each of the above embodiments, in the opening process, the switch 22 may be transitioned to the closed state when the capacitor voltage Vc and the battery voltage V0 are not the same. For example, the switch 22 may be configured to transition to the closed state when the capacitor voltage Vc becomes a predetermined value lower than the battery voltage V0. In this configuration, when the switch 22 is switched to the closed state, it is possible to reliably prevent a back electromotive force from being generated in the motor 12 due to the battery voltage V0 being low.

In each of the above embodiments, the current command values Id* and Iq* may be calculated by feedforward control. The current command values Id* and Iq* may also be calculated using correlation information such as a map or a function.

In each of the above embodiments, the capacitor provided between the power switch and the power conversion unit includes a Y capacitor in addition to the smoothing capacitor 21. An example of a configuration in which the power conversion device 13 has a Y capacitor is a configuration in which the Y capacitor is connected to the P line 25 or N line 26 between the switch 22 and the inverter 30.

<Common>
In each of the above embodiments, as long as the current flowing through each of the windings 12a of the multiple phases can be individually controlled, the conversion circuit 31 does not need to be provided for each of the multiple phases. For example, for the multiple phase conversion circuit 31 included in the inverter 30, one of the arm circuits 32, 35 may be common to at least two phases. As shown in FIG. 22, for the three-phase conversion circuit 31, the second arm circuit 35 of the arm circuits 32, 35 may be common to the U phase, V phase, and W phase. In this configuration, the first arm circuit 32 is provided individually for each of the U phase, V phase, and W phase. Therefore, the inverter 30 includes three first arm circuits 32, while the inverter 30 includes only one second arm circuit 35.

Even with this configuration, it is possible to perform two-phase control when an abnormality occurs in the arm switch 33 of the first arm circuit 32. For example, when an abnormality occurs in the arm switch 33 of the first arm circuit 32 for one of the U-phase, V-phase, and W-phase, the control device 40 performs two-phase control with the arm switches 33 of the first arm circuits 32 for the remaining two phases as the control targets. In this case, it is preferable that the arm switch 36 of the second arm circuit 35 is turned on and off in accordance with the on and off of the arm switch 33 of the first arm circuit 32.

In a configuration in which one of the arm circuits 32, 35 is shared by at least two phases, the cost burden can be reduced for the arm circuits 32, 35 that are reduced by sharing. For example, in a configuration in which one of the arm circuits 32, 35 for a three-phase conversion circuit 31 is shared by three phases, the cost burden can be reduced for the arm circuits 32, 35 for two phases that are reduced by sharing.

In the first embodiment, in steps S302 and S311 from the second time onward in the opening process, the q-axis current command value Iq* may be set to a predetermined specific value. The specific value is information acquired by testing, simulation, or the like, and is stored in the storage unit of the control device 40. For example, in the voltage increase process including step S302, the specific value is set to a value at which the motor 12 regenerates, regardless of the operating state of the motor 12, such as the motor rotation speed Nm. That is, the specific value is set to a value at which the capacitor voltage Vc increases. On the other hand, in the voltage decrease process including step S311, the specific value is set to a value at which the motor 12 powers, regardless of the operating state of the motor 12. That is, the specific value is set to a value at which the capacitor voltage Vc decreases.

In each of the above embodiments, abnormalities that may occur in the conversion circuit 31 include short circuit abnormalities and open circuit abnormalities in the arm switches 33 and 36, as well as breaks and short circuits in the wiring connected to the arm switches 33 and 36.

In each of the above embodiments, the current sensor 28 does not have to detect the current flowing through the winding 12a for all three phases. For example, the current sensor 28 may output detection signals for two of the three phases, the current calculation unit of the control device 40 may calculate the phase currents for the two phases corresponding to the detection signals, and the phase current for the remaining phase may be estimated from the phase currents of the two phases.

In each of the above embodiments, the control device 40 is provided by a control system including at least one computer. The control system includes at least one processor (hardware processor) that is hardware. The hardware processor can be provided by the following (i), (ii), or (iii).

(i) The hardware processor may be a hardware logic circuit. In this case, the computer is provided by digital circuits including a large number of programmed logic units (gate circuits). The digital circuits may include a memory that stores at least one of a program and data. The computer may be provided by analog circuits. The computer may be provided by a combination of digital and analog circuits.

(ii) The hardware processor may be at least one processor core that executes a program stored in at least one memory. In this case, the computer is provided with at least one memory and at least one processor core. The processor core is referred to as a CPU, for example. The memory is also referred to as a storage medium. The memory is a non-transitive and tangible storage medium that non-transiently stores "at least one of a program and data" that can be read by the processor.

(iii) The hardware processor may be a combination of (i) and (ii) above, where (i) and (ii) are located on different chips or on a common chip.

In other words, at least one of the means and functions provided by the control device 40 can be provided by hardware only, software only, or a combination of both.

In each of the above embodiments, the motor 12 may have a stator including a permanent magnet that forms a field magnet, and a rotor including a winding 12a that forms an armature.

In each of the above embodiments, the vehicle equipped with the power conversion device 13 includes a passenger car, a bus, a construction vehicle, an agricultural machinery vehicle, etc. Furthermore, a vehicle is one type of moving body, and in addition to a vehicle, other moving bodies equipped with the power conversion device 13 include trains and airplanes. Examples of the power conversion device 13 include an inverter device and a converter device. Examples of this converter device include an AC input/DC output power supply device, a DC input/DC output power supply device, and an AC input/AC output power supply device.

<Characteristics of composition group A>
The configurations disclosed in this specification include the features of configuration group A as follows.

[Feature A1]
A power conversion device (13) for converting power supplied from a power supply unit (11) to a motor (12) having a multi-phase winding (12a) from direct current to alternating current by a power conversion unit (30) having a multi-phase conversion circuit (31) connected to each of the multi-phase windings,
a reference control unit (S113, S114) for controlling the power conversion unit so that a phase difference (PD3) between currents flowing through windings of a plurality of phases becomes a reference value;
a phase change unit (S203 to S205, S401, S501, S502) that controls the power conversion unit so that, when an abnormality occurs in at least one conversion circuit, the phase difference between currents passed through windings by the remaining conversion circuits of at least two phases is set as an abnormality phase difference (PD2) and the abnormality phase difference is changed from a reference value to a changed value;
A power conversion device comprising:

[Feature A2]
The phase change unit is
The power conversion device according to feature A1, further comprising a cutoff execution unit (S205, S401, S501, S502) that cuts off current to a winding connected to the conversion circuit in which an abnormality has occurred.

[Feature A3]
The power conversion device according to feature A1 or A2, wherein when the phase difference during an abnormality is changed from a reference value to a changed value by the phase change unit, a rotating magnetic field (MFR) caused by currents flowing through the windings of the remaining at least two phases of the conversion circuits becomes closer to a circle in shape than when the phase difference during an abnormality remains at the reference value.

[Feature A4]
The power conversion device according to any one of features A1 to A3, wherein the change value is a value that causes a rotating magnetic field (MFR) caused by currents flowing through windings of at least two remaining phases of the conversion circuits to become circular.

[Feature A5]
The motor is a three-phase motor having three phase windings;
The power conversion unit has a three-phase conversion circuit,
The reference control unit controls the power conversion unit with a reference value of 120 degrees,
The power conversion device according to any one of features A1 to A4, wherein the phase change unit controls the power conversion unit by setting the change value to 60 degrees when an abnormality occurs in a one-phase conversion circuit.

[Feature A6]
The phase change unit is
The power conversion device according to any one of features A1 to A5, further comprising a voltage command unit (S203) that sets voltage command values (Vu*, Vv*, Vw*) that are command values for voltages applied to the windings so that the phase difference during an abnormality is changed from a reference value to a changed value.

[Feature A7]
The phase change unit is
A power conversion device according to any one of features A1 to A6, in which, when an abnormality occurs in one of a first switch (33) connected to one end of the winding in the conversion circuit and a second switch (36) connected to the other end of the winding, the power conversion unit is controlled as if an abnormality has occurred in the conversion circuit.

[Feature A8]
The phase change unit is
The power conversion device according to feature A7, further comprising a winding opening unit (S401, S501, S502) that transitions a winding switch (59) that connects at least one of the first switch and the second switch to the winding to an open state for a conversion circuit in which an abnormality has occurred.

[Feature A9]
The phase change unit is
A power conversion device according to any one of features A1 to A8, which has a conversion opening unit (S205) that transitions all of the remaining conversion switches to an open state when an abnormality occurs in at least one of a plurality of conversion switches (33, 36) connected to the windings in the conversion circuit.

[Feature A10]
The power conversion device according to any one of features A1 to A9, wherein the phase change unit controls the power conversion unit so that the abnormal phase difference is changed from a reference value to a changed value when the motor rotation speed (Nm) is equal to or lower than a predetermined rotation threshold value (Nth).

<Characteristics of composition group B>
The configurations disclosed in this specification include the features of configuration group B as follows.

[Feature B1]
A power conversion device (13) that converts power supplied from a power supply unit (11) to a motor (12) having a multi-phase winding (12a) from direct current to alternating current by a power conversion unit (30) having a multi-phase conversion circuit (31) connected to each of the multi-phase windings,
a coordinate conversion unit (42) for converting a current flowing through the winding into a d-axis current (Id) and a q-axis current (Iq) in a dq coordinate system;
an open transition unit (S106) that transitions a power switch (22) that electrically connects the power supply unit and the power conversion unit to an open state when an abnormality occurs in at least one phase of the conversion circuit;
a voltage increasing unit (S302) that sets a q-axis current command value (Iq*) of a q-axis current such that a capacitor voltage (Vc) of a capacitor (21) provided between the power switch and the power conversion unit increases above a power supply voltage (V0) of the power supply unit when the power switch is transitioned to an open state by the open transition unit;
an open control unit (S303 to S305, S312 to S314) that controls the power conversion unit so that the remaining conversion circuits of at least two phases pass currents through the windings in accordance with the q-axis current command value set by the voltage increasing unit when the power switch is transitioned to an open state by the open transition unit;
A power conversion device comprising:

[Feature B2]
The power conversion device according to feature B1, wherein the open transition unit transitions the power switch to an open state when the motor rotation speed (Nm) is greater than a predetermined open threshold (Nth).

[Feature B3]
The power conversion device according to feature B2, wherein the open threshold is a rotation speed at which the motor can be driven by the remaining at least two-phase conversion circuits when an abnormality occurs in the conversion circuit of at least one phase and the power switch of the remaining conversion circuits is in a closed state.

[Feature B4]
The power conversion device according to any one of features B1 to B3, wherein the voltage increasing unit sets the q-axis current command value by feedback control so that the capacitor voltage becomes a capacitor threshold value (Vh) that is higher than the power supply voltage.

[Feature B5]
The power conversion device according to Feature B4, wherein the capacitor threshold is an upper limit of a voltage applied to the power conversion unit.

[Feature B6]
The power conversion device according to any one of features B1 to B5, further comprising a d-axis current command unit (S301, S310) that sets a d-axis current command value (Id*) of the d-axis current so that the motor rotation speed (Nm) decreases when the power switch is transitioned to an open state by the open transition unit.

[Feature B7]
The power conversion device according to feature B6, wherein the d-axis current command unit sets the d-axis current command value according to the capacitor voltage in addition to the motor rotation speed.

[Feature B8]
A power conversion device according to any one of features B1 to B7, comprising a close transition unit (S318) that transitions the power switch to a closed state when the motor rotation speed (Nm) decreases to a predetermined close threshold (Nth).

[Feature B9]
A voltage reducing unit (S311) that sets a q-axis current command value so that a capacitor voltage is reduced when the rotation speed of the motor is reduced to a closing threshold value;
The power conversion device according to feature B8, wherein the close transition unit transitions the power switch to a closed state when the q-axis current command value is set by the voltage lowering unit and the capacitor voltage drops to the power supply voltage.

[Feature B10]
The power conversion device according to feature B9, wherein the voltage lowering unit sets the q-axis current command value by feedback control so that the capacitor voltage becomes the power supply voltage.

[Feature B11]
a reference control unit (S113, S114) for controlling the power conversion unit so that a phase difference (PD3) between currents flowing through windings of a plurality of phases becomes a reference value;
The power conversion device according to any one of features B1 to B10, wherein the open control unit controls the power conversion unit so that the phase difference during an abnormality (PD2) is changed from a reference value to a changed value, the phase difference being a phase difference during an abnormality between the currents passed through the windings by the remaining two-phase conversion circuits.

<Constituent Group A>
11...battery as power supply unit, 12...motor, 12a...winding, 13...power conversion device, 30...inverter as power conversion unit, 31...conversion circuit, 33...arm switch as first switch and conversion switch, 36...arm switch as second switch and conversion switch, 59...winding switch, PD2...phase difference as phase difference during abnormality, PD3...phase difference, MFR...rotating magnetic field, Vu*...U-phase voltage command value, Vv*...V-phase voltage command value, Vw*...W-phase voltage command value, S113, S114...reference control unit, S203...phase change unit and voltage command unit, S204...phase change unit, S205...phase change unit, cut-off execution unit and conversion opening unit, S401, S501, S502...phase change unit, cut-off execution unit and winding opening unit.

<Composition group B>
11...battery as power supply unit, 12...motor, 12a...winding, 13...power conversion device, 21...smoothing capacitor as capacitor, 22...switch as power switch, 30...inverter as power conversion unit, 31...conversion circuit, 42...three-phase to two-phase conversion unit as coordinate conversion unit, Id...d-axis current, Id*...d-axis current command value, Iq...q-axis current, Iq*...q-axis current command value, Nm...motor rotation speed as rotation speed, Nth...rotation threshold as open threshold and close threshold, PD2... Phase difference as phase difference during abnormality, PD3...phase difference, V0...battery voltage as power supply voltage, Vc...capacitor voltage, Vh...capacitor upper limit value as capacitor threshold, S106...open transition section, S113, S114...reference control section, S301...d-axis current command section, S302...voltage increase section, S303 to S305...open control section, S310...d-axis current command section, S311...voltage decrease section, S312 to S314...open control section, S318...close transition section, S501, S502...phase change section.

Claims (11)

A power conversion device (13) for converting power supplied from a power supply unit (11) to a motor (12) having a multi-phase winding (12a) from direct current to alternating current by a power conversion unit (30) having a multi-phase conversion circuit (31) connected to each of the multi-phase windings,
a reference control unit (S113, S114) for controlling the power conversion unit so that a phase difference (PD3) between currents flowing through the windings of the multiple phases becomes a reference value;
a phase change unit (S203 to S205, S401, S501, S502) that controls the power conversion unit such that, when an abnormality occurs in at least one of the conversion circuits, a phase difference between currents that are passed through the windings by the remaining conversion circuits of at least two phases is set as an abnormality phase difference (PD2), and the abnormality phase difference is changed from the reference value to a changed value;
Equipped with
The phase change unit is
The power conversion device has a winding opening unit (S401, S501, S502) that switches a winding switch (59) connecting the conversion circuit and the winding to an open state for the conversion circuit in which an abnormality has occurred . A power conversion device (13) for converting power supplied from a power supply unit (11) to a motor (12) having a multi-phase winding (12a) from direct current to alternating current by a power conversion unit (30) having a multi-phase conversion circuit (31) connected to each of the multi-phase windings,
a reference control unit (S113, S114) for controlling the power conversion unit so that a phase difference (PD3) between currents flowing through the windings of the multiple phases becomes a reference value;
a phase change unit (S203 to S205, S401, S501, S502) that controls the power conversion unit so that, when an abnormality occurs in one of a first switch (33) connected to one end of the winding and a second switch (36) connected to the other end of the winding in the conversion circuit of at least one phase, the phase difference between currents passed through the windings by the conversion circuits of at least two remaining phases is set as an abnormality phase difference (PD2) and the abnormality phase difference is changed from the reference value to a changed value, assuming that an abnormality has occurred in the conversion circuit of at least one phase;
Equipped with
The phase change unit is
The power conversion device has a winding opening unit (S401, S501, S502) that transitions a winding switch (59) that connects at least one of the first switch and the second switch to the winding to an open state for the conversion circuit in which an abnormality has occurred . 3. The power conversion device according to claim 1, wherein the phase change unit controls the power conversion unit so that the abnormality-time phase difference is changed from the reference value to a changed value when a rotation speed (Nm) of the motor is equal to or lower than a predetermined rotation threshold (Nth) . A power conversion device (13) for converting power supplied from a power supply unit (11) to a motor (12) having a multi-phase winding (12a) from direct current to alternating current by a power conversion unit (30) having a multi-phase conversion circuit (31) connected to each of the multi-phase windings,
a reference control unit (S113, S114) for controlling the power conversion unit so that a phase difference (PD3) between currents flowing through the windings of the multiple phases becomes a reference value;
a phase change unit (S203 to S205, S401, S501, S502) that controls the power conversion unit such that, when an abnormality occurs in at least one of the conversion circuits, a phase difference between currents that are passed through the windings by the remaining conversion circuits of at least two phases is set as an abnormality phase difference (PD2), and the abnormality phase difference is changed from the reference value to a changed value;
Equipped with
The phase change unit controls the power conversion unit so that the abnormality phase difference is changed from the reference value to a changed value when the rotation speed (Nm) of the motor is equal to or lower than a predetermined rotation threshold (Nth) . The phase change unit is
5. The power conversion device according to claim 4, wherein when an abnormality occurs in one of a first switch (33 ) connected to one end of the winding in the conversion circuit and a second switch (36) connected to the other end of the winding, it is determined that an abnormality has occurred in the conversion circuit and the power conversion unit is controlled. The phase change unit is
The power conversion device according to any one of claims 1 to 5 , further comprising a cutoff execution unit (S205, S401, S501, S502) that cuts off current to the winding connected to the conversion circuit in which an abnormality has occurred. The power conversion device according to any one of claims 1 to 6, wherein when the phase difference during an abnormality is changed from the reference value to the changed value by the phase change unit, a rotating magnetic field (MFR) caused by currents passed through the windings by the conversion circuits of at least two remaining phases becomes closer to a circle than when the phase difference during an abnormality remains at the reference value. The power conversion device according to claim 1 , wherein the change value is a value that causes a rotating magnetic field (MFR) caused by currents flowing through the windings of the remaining at least two phases of the conversion circuits to become circular. the motor is a three-phase motor having three phases of the windings,
The power conversion unit has a three-phase conversion circuit,
The reference control unit controls the power conversion unit with the reference value set to 120 degrees,
The power conversion device according to claim 1 , wherein the phase changer controls the power conversion unit by setting the change value to 60 degrees when an abnormality occurs in the conversion circuit of one phase. The phase change unit is
The power conversion device according to any one of claims 1 to 9, further comprising a voltage command unit (S203 ) that sets voltage command values (Vu*, Vv*, Vw*) that are command values for voltages applied to the windings so that the abnormality-time phase difference is changed from the reference value to the changed value. The phase change unit is
The power conversion device according to any one of claims 1 to 10, further comprising a conversion opening unit (S205) that, when an abnormality occurs in at least one of a plurality of conversion switches (33, 36 ) connected to the winding in the conversion circuit, transitions all of the remaining conversion switches to an open state.

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