JP2001327173A - PWM inverter for motor control - Google Patents

Abstract

(57) [Problem] To provide a PWM inverter for obtaining a phase current to be used for feedback control from a DC bus current, and to be able to reliably detect a DC bus current corresponding to each phase even when voltage commands between the phases are close to each other. I do. SOLUTION: v-phase and w-phase first voltage command values vv1 *
, Vw1 * are close to each other, as shown in FIG.
In the first half of the WM cycle, the third w phase is changed from vw1 * to vcmp.
Offset by 23 and the difference from the v-phase is Dmin,
In the latter half of the cycle, vw1 * is corrected to be offset by vcmp23 in the reverse direction, and Pw is set as a second voltage command value.
Generate a WM pulse. By the above correction, the falling and rising timing intervals ΔT between the phases of the PWM pulses are secured as shown in (c), and the DC bus current Is during the switching by each pulse can be detected, as shown in (d). The phase currents iu, iv, iw of each phase can be determined clearly.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor control inverter for performing feedback control of a motor using a phase current of the motor.

[0002]

2. Description of the Related Art In order to drive a three-phase motor with a DC power supply,
An inverter of current control by PWM (pulse width modulation) that performs feedback control of the motor current using the phase current of the motor is used. In such a current control PWM inverter, a control command is given as a current command value, which is converted into a voltage command value, and then a PWM control signal for the switching elements of each phase of the main circuit is generated. Then, the phase current value of each phase is fed back to adjust the voltage command value.

[0003] Regarding the phase current of each phase, for example, in the PWM inverter disclosed in JP-A-8-19263, immediately before and after switching of the switching element of each phase of the inverter main circuit, the current sensor detects the phase current of the inverter main circuit. A DC bus current is detected, and a change in the detected current is distributed to each phase in accordance with the switching timing, thereby obtaining a detected current for each phase. Thus, it is expected that the current detection for each phase can be completed by one current sensor.

[0004]

Generally, in a PWM inverter, the voltage command value may be 0 for all three phases, or the voltage command values for two phases may be substantially equal. As a result, for example, when the three-phase switching elements switch simultaneously, the former occurs, and when the two-phase switching elements simultaneously switch, the latter occurs. 6A and 6B show a specific example, in which (a) shows a voltage command value and a comparison triangular wave, (b) shows a PWM pulse, and (c) shows a change in a DC bus current. As shown in (a), when the value of the v-phase voltage command value vv * and the value of the w-phase voltage command value vw * of the three phases u, v, and w are the same, PWM generated by triangular wave comparison is used.
As for the pulse, the rising and falling of the v-phase voltage and the w-phase voltage, that is, the switching, respectively, are simultaneous as shown in FIG.

However, in the conventional PWM inverter that detects the DC bus current with one current sensor, the DC bus current before and after switching of the switching element of each phase is sampled and held, and the difference between the detected values is used to determine the corresponding phase. Since the current value is obtained, if the rise and fall of the v-phase voltage and the w-phase voltage are simultaneous, the time during which the current information of each phase appears on the DC bus is short, making it difficult to detect.
As shown in FIG. 6C, the v-phase current and the w-phase current cannot be separated. This is true not only when the switching is completely simultaneous, but also when the interval between the switching of one phase and the switching of the other phase is short, and it is difficult or impossible to detect the DC bus current during the switching. There is a problem in that the accuracy is lowered, and thus the current of each phase cannot be obtained properly.

Accordingly, the present invention has been made in view of the above problems, and in a motor control inverter for obtaining a phase current to be used for feedback control from a DC bus current, even if switching timings between the phases overlap, each phase current is appropriately adjusted. It is an object of the present invention to provide a motor control inverter which can be obtained as follows.

[0007]

According to the present invention, there is provided a current control unit for outputting a three-phase first voltage command value by current control, and a PWM based on the first voltage command value.
A PWM bus for motor control, comprising: a PWM pulse generating means for outputting a pulse; and an inverter main circuit for driving the motor controlled by the PWM pulse, wherein the motor control PWM inverter feeds back a phase current of the motor to a current control unit. And a phase current calculation unit that calculates a phase current based on a detection value of the current sensor and a PWM pulse output from the PWM pulse generation unit, and the PWM pulse generation unit includes a PWM signal between each phase. The PWM pulse is output by setting the timing interval of the rising or falling of the pulse to a predetermined value or more. Since the timing interval between the rising and falling phases of the PWM pulse output by the PWM pulse generation means is ensured, the DC bus current corresponding to each phase is reliably detected, and the phase current can be calculated.

According to a second aspect of the present invention, when the difference between the phases arranged in the order of the magnitude of the first voltage command value is smaller than a predetermined interval value, the PWM pulse generation means sets two small values of the difference every one PWM cycle. At least one value of the first voltage command value of the phase is corrected to a second voltage command value having the same value and the same average value and different values in the first half and the second half of the cycle. A voltage command correction unit for setting the difference equal to or greater than a predetermined interval value;
That outputs a PWM pulse according to the voltage command value of
And an M pulse generator. More specifically, as set forth in claim 3, the voltage command correction unit increases the first voltage command value of at least one of the two phases in which the difference is small in the first half of the 1 PWM cycle by enlarging the difference. And the first voltage command value is corrected in the reverse direction by the predetermined value in the second half of the cycle to obtain a second voltage command value.

In order for the PWM pulse generation means to output a PWM pulse in which the timing interval between phases is secured, the first
This can be achieved by providing a voltage command correction unit that corrects the voltage command value of (1) to the second voltage command value. The voltage command correction unit widens the PWM pulse timing interval by correcting the first voltage command value of one of the adjacent phases to obtain a second voltage command value having a larger difference between the command values. Also,
Since the corrected command value is made different between the first half and the second half so that the average value is the same as before correction, the timing interval of the PWM pulse is secured while maintaining the same level as the first voltage command value in one entire cycle.

According to a fourth aspect of the present invention, as a correction in the first half of one PWM cycle, two phases having a small difference are the first phase.
When a phase of the largest voltage command value is included, a predetermined value is added to the first voltage command value of the largest value, and two phases with a small difference are the smallest value of the first voltage command value. , A predetermined value is subtracted from the smallest value of the first voltage command value. Thereby, the second obtained by the correction
Of the voltage command value approaches a phase having a sufficient interval before the correction, and the difference between the phases is smaller than the predetermined interval value.

According to a fifth aspect of the present invention, when the voltage command correction section determines that the difference between the three phases arranged in the order of the magnitude of the first voltage command value is smaller than a predetermined interval value between adjacent ones, the 1PW
The first voltage command values of the two phases selected in the first half of the M cycle are corrected by the first predetermined value and the second predetermined value, respectively, so that the adjacent phases of the three phases are set to the predetermined interval value. The first voltage command values of the two phases selected by the first predetermined value and the second predetermined value are corrected in the reverse direction to obtain a second voltage command value. In particular, even when all of the three phases are smaller than the predetermined interval value, the correction is made so that each of the phases of the second voltage command value becomes the predetermined interval value, so that the DC bus current corresponding to each phase is reliably detected. And the phase current can be calculated.

According to a sixth aspect of the present invention, in the configuration of the fifth aspect, the two phases particularly selected are the phase of the largest value and the smallest value of the first voltage command value, and the correction in the first half of one PWM cycle is The first predetermined value is added to the largest first voltage command value, and the second predetermined value is subtracted from the smallest first voltage command value. This allows
The first predetermined value and the second predetermined value can be expanded to a predetermined interval value between each phase with a minimum value, and the timing of the PWM pulse is reduced while reducing the amount of change from the first voltage command value as a correction amount. By increasing the interval, each phase current can be obtained.

According to a seventh aspect of the present invention, there is provided a current control unit for outputting three-phase first voltage command values by current control to two sets of motors, and correcting the first voltage command value to obtain a second voltage command value. A voltage command correction unit that outputs a voltage command value of the same, a PWM pulse generation unit that outputs a PWM pulse based on the second voltage command value, and an inverter main circuit that drives the motor under the control of the PWM pulse. In a motor control PWM inverter in which each inverter main circuit is supplied with power from a DC power supply via a common DC bus and feeds back a phase current of each motor to a corresponding current control unit, a current sensor is provided on the DC bus. In addition, the phase current is determined by the detection value of the current sensor and the PW output from the PWM pulse generator.
And a phase current calculation unit for calculating based on the M pulse. Each of the voltage command correction units is arranged between the phases adjacent to each other in the six phases arranged in the order of the magnitude of the first voltage command values from both current control units. When there is a difference smaller than the predetermined interval value, 1PW
In the first half of the M period, each voltage command correction unit sets the corresponding first voltage command value with a predetermined value set for each phase so that the difference between the six adjacent phases is equal to or greater than a predetermined interval value. Corrected, in the second half of the cycle,
Is corrected in the reverse direction by a predetermined value set for each of the above phases to obtain a second voltage command value. Inverter main circuits of two sets of motors share a DC power supply, and in each voltage command correction unit, a predetermined interval value is set between adjacent phases in six phases arranged in the order of magnitude of first voltage command values from both current control units. As described above, the DC bus current corresponding to each phase is reliably detected by one current sensor, and the phase current can be obtained based on the detected current.

Preferably, the predetermined interval value in the voltage command value is limited to a voltage difference corresponding to a time required for the current sensor to detect the current of the DC bus, as described in claim 8.

[0015]

Embodiments of the present invention will be described below with reference to examples. FIG. 1 is a block diagram showing the overall configuration of the embodiment. A motor 5 is connected to a DC power supply 2 via a three-phase bridge circuit 3 including six switching elements 4 to form an inverter main circuit 1. The three-phase bridge circuit 3 outputs phase currents iu, iv, iw to the motor 5. The DC power supply 2 is provided with a capacitor 6 in parallel with the three-phase bridge circuit 3 to stabilize the DC voltage supplied to the three-phase bridge circuit 3.

For controlling the inverter main circuit 1, a current control unit 10 for receiving a current command value from the outside as a motor drive command is provided, and a voltage command correction unit 11 and a PWM pulse generation unit 12 are sequentially connected to the current control unit 10. Have been.
The current controller 10 controls the first voltage command values vu1 *, vv1 *, vw of each phase based on the current command value and a phase current described later.
Outputs 1 *. The voltage command correction unit 11 corrects the first voltage command value and corrects the second voltage command values vu2 *, vv2 *,
Output vw2 *. The PWM pulse generation unit 12
And outputs a PWM pulse signal for turning on and off the switching element 4 of the three-phase bridge circuit 3 based on the voltage command value of

A current sensor 13 is provided on the DC bus 8 from the DC power supply 2 to the three-phase bridge circuit 3, and the current sensor 13 is connected to a phase current calculation unit 14. The phase current calculation unit 14 is connected to the PWM pulse generation unit 12 and the current control unit 10, and based on the DC bus current Is detected by the current sensor 13 and the PWM pulse signal from the PWM pulse generation unit 12, Phase currents iu, iv,
iw is calculated and output to the current control unit 10 as feedback information.

The voltage command correction unit 11 sets the first voltage for each phase to such an extent that the switching interval between the phases of the switching element 4 of the three-phase bridge circuit 3 becomes short and it becomes difficult to detect the DC bus current during switching. When the difference between the command values is small, the second voltage command value is corrected by increasing the switching interval between phases. FIG. 2 and FIG. 3 are flowcharts showing the flow of the generation of the second voltage command value for each PWM cycle in the voltage command correction unit 11. First, in step 101, the order of magnitudes of the first voltage command values vu1 *, vv1 *, vw1 * output from the current control unit 10 is checked. Here, the first largest value is called a maximum phase voltage command value vmax1 *, the second largest value is called a second phase voltage command value vm1 *, and the third value is called a minimum phase voltage command value vmin1 *.

In step 102, the maximum phase voltage command value vmax1 * and the second phase voltage command value vm
The difference Δv12 of 1 * is obtained, and in the next step 103, it is checked whether the difference Δv12 of the command value is equal to or more than a predetermined value Dmin. Here, the predetermined value Dmin is set in advance as a value corresponding to a time interval sufficient for detecting the DC bus current Is. The difference Δv12 between the command values is a predetermined value Dm
If it is not less than "in", the process proceeds to step 105;

In step 104, the correction amount is set to vcmp1.
2 = Dmin-Δv12 Step 1
In 05, since there is no need for correction, vcmp12 = 0. In step 106, the maximum phase voltage command value vmax
The correction amount vcmp12 is added to 1 * to obtain a correction value (second voltage command value) vmax2f * in the first half of the PWM cycle corresponding to the first largest phase of the first voltage command value. When the interval is widened by subtracting the correction amount from the second phase voltage command value, the reduced second phase voltage command value may approach the minimum phase voltage command value more than the predetermined value Dmin. Therefore, here, the interval is widened by correcting the maximum phase voltage command value to make it even larger.

Next, at step 107, the difference Δv23 between the second phase voltage command value vm1 * and the minimum phase voltage command value vmin1 * is determined. At the next step 108, the difference Δv23 between the command values is equal to or more than the predetermined value Dmin. Check whether or not. When the difference Δv23 between the command values is equal to or larger than the predetermined value Dmin, the process proceeds to step 110, and when smaller than the predetermined value Dmin, the process proceeds to step 109. In step 109, the correction amount is set to vcmp23 = Dmin-Δv23. On the other hand, in step 110, since there is no need for correction, vcmp23 = 0.

Then, in the next step 111,
Correction amount vcmp23 from minimum phase voltage command value vmin1 *
Is subtracted to obtain a correction value (second voltage command value) vmin for the first half of the PWM cycle corresponding to the third phase of the first voltage command value.
2f *. When the interval is increased by adding the correction amount to the second phase voltage command value, the increased second phase voltage command value may approach the maximum phase voltage command value more than the predetermined value Dmin. Here, the interval is widened by correcting the minimum phase voltage command value to make it even smaller.

Subsequently, in step 112, the second largest second-phase voltage command value vm1 * is directly used as the PWM of the phase.
The correction value (second voltage command value) vm2f * in the first half of the cycle is set. In step 113, steps 106 and 11 described above are performed.
The correction values vmax2f * and vmi obtained in steps 1 and 112
n2f *, vm2f * are set as second voltage command values vu2 *, vv2 *, vw2 * in the first half of the PWM cycle, and P
Output to the WM pulse generation unit 12.

Next, a second voltage command value in the latter half of the PWM cycle is obtained. First, in step 114, the correction amount vcmp12 is subtracted from the maximum phase voltage command value vmax1 * to obtain a correction value (second voltage command value) vmax2r * corresponding to the first largest phase of the first voltage command value. . In step 115, the correction amount vcmp23 is added to the minimum phase voltage command value vmin1 *, and a correction value (second voltage command value) vmin2r * corresponding to the third phase of the first voltage command value is obtained.
And Then, in step 116, the second largest second-phase voltage command value vm1 * is directly used as the correction value (second voltage command value) vm2r * of the phase.

In step 117, the above-mentioned step 11
Correction values vmax2r *, vmi obtained in 4 to 115
n2r *, vm2r * are set as second voltage command values vu2 *, vv2 *, vw2 * in the latter half of the PWM cycle,
Output to the WM pulse generation unit 12. The above vmax2r *
And vmin2r * are set by subtracting and adding the correction amounts added or subtracted in the first half of the PWM cycle in the reverse direction, respectively, and thus correspond to the first largest phase and the third phase of the first voltage command value. The average value of each second voltage command value over the first and second half of the PWM cycle is the same as the first voltage command value.

The first voltage command value output from the current control unit 10 is corrected to the second voltage command values vu2 *, vv2 *, vw2 * by the voltage command correction unit 11, and the PW
Since the signal is input to the M-pulse generator 12, the ON / OFF timing of the switching element 4 of the three-phase bridge circuit 3 is separated between the phases, so that the DC bus current Is during switching can be reliably detected. FIG. 4 is a waveform chart showing this separation state. (A) shows a first voltage command value and a comparison triangle wave, (b) shows a second voltage command value and a comparison triangle wave, and (c)
Indicates a PWM pulse, and (d) indicates a change in DC bus current. Here, as shown in (a), the value of the u-phase first voltage command value vu1 * is the largest, and the v-phase and w-phase first voltage command values vv1 * and vw1 * are sufficiently separated therefrom. vv1
*> Vw1 * and are close to each other.

(B) shows a second voltage command value, which is PWM
In the first half of the cycle, the third phase is from vw1 * to vcmp23
= Dmin-Δv23 minus vw2 *.
Here, Δv23 = vv1 * −vw1 *. The values of the second voltage command values vu2 *, vv2 * of the other phases are the same as the first voltage command values. The difference between vw2 * and vv2 * is Dm
in. In the latter half of the PWM cycle, the third phase is v
vw2 * is a value obtained by adding vcmp23 to w1 *. The values of the second voltage command values vu2 *, vv2 * of the other phases are the same as the first voltage command values as in the first half.

As shown in FIG. 3C, the PWM pulse generated by the triangular wave comparison from the second voltage command value is such that vw2 * and vv2 * are separated by Dmin in the first half of the 1PWM cycle, and as a result, , V-phase and w-phase pulses fall and rise timing intervals ΔT are secured. As a result, as shown in (d), the DC bus current Is during switching by each pulse can be detected, and the phase current iu and the phase currents iv and iw can be clearly determined in the phase current calculation unit 14. Can be sought. In the latter half of the lPWM cycle, vv2 * and vw2
* (= Vw1 * + vcmp23) is smaller than Dmin, so that the DC bus current I
It is preferable to set the value of Dmin so that s can be detected. However, even when Dmin is set to the minimum value capable of detecting the DC bus current, the timing interval ΔT is secured in the first half of the PWM cycle and the DC bus current Is is detected. It can be used as a DC bus current.

The case where the first and second voltage command values are close to each other has been described above. However, the first and second first voltage command values are close to each other. The same applies to the case or when all of the first voltage command values are close to each other.

The present embodiment is configured as described above, and the phase currents iu, iv, i of the motor 5 used for feedback control.
In a PWM inverter that calculates w from the DC bus current Is, if there are three first-phase command voltage values generated by the current control unit 10 that are close to each other, the three-phase first voltage command values are separated by a predetermined value Dmin. Since the PWM pulse is corrected and converted to the offset second voltage command value and the PWM pulse is generated based on the second voltage command value, the switching in the three-phase bridge circuit 3 may overlap at the same time. Also, a predetermined timing interval is secured between the switching operations, and the DC bus current Is is maintained between the switching operations.
Can be reliably detected, and the phase currents iu, iv, iw of each phase can be calculated.

Further, the separation offset of the predetermined value Dmin is limited to the first half of the PWM cycle, and the second voltage command value in the second half is corrected to a value offset by the same amount to the opposite side. Since the average of the whole passed is the same as the first voltage command value, the driving itself of the motor 5 is not affected at all.

FIG. 5 shows a second embodiment. In this embodiment, one current sensor provided on the DC bus of two sets of current-controlled PWM inverters sharing a DC power supply calculates the phase currents of two sets of motors. The three-phase bridge circuits 3A and 3B of each of the motors 5A and 5B have the same current control units 10A and 10B as in the first embodiment.
B, the voltage command correction units 11A and 11B and the PWM pulse generation units 12A and 12B are connected, and the three-phase bridge circuits 3A and 3B are connected to a common DC power supply 1. The voltage command correction units 11A and 11B are connected to each other, and receive information on the first voltage command value from the corresponding current control units 10A and 10B.
To be sent to

The DC bus 8 from the DC power supply 1 to the three-phase bridge circuit is provided with one current sensor 13 before branching to the two three-phase bridge circuits 3A and 3B. 16 are connected. The phase current calculator 16 is common to the two motors 5A and 5B,
PWM pulse signals are input from the WM pulse generation units 12A and 12B, and the phase current iu to each of the motors 5A and 5B is
a, iva, iwa, and iub, ivb, iwb
And outputs this to the corresponding current control units 10A and 10B as feedback information.

Each of the voltage command correction units 11A and 11B
The first voltage command values from current control units 10A and 10B are corrected so that the difference between the two sets of six voltage command values to M pulse generation units 12A and 12B is equal to or greater than a predetermined value. That is, in each voltage command correction unit, both current control units 1
First voltage command value vu output from 0A and 10B
1a *, vv1a *, vw1a *, vu1b *, vv1b *, vw
Check the size order of 1b *.

Among these, first, the difference between two vm13 * and vm14 * whose values are close to 0 is a predetermined value Dmin.
Otherwise, one of the values, for example, vm13 * is changed so that the difference becomes Dmin, and the second voltage command value v
m23 *. When the difference is equal to or greater than the predetermined value Dmin, the value of vm13 * is directly used as the second voltage command value vm23 *
And

Subsequently, vm23 * is compared with an adjacent value vm12 * in the direction of increasing the value. If the difference is small, the larger value vm12 * is changed (corrected) so that the difference becomes Dmin. It is assumed that the voltage command value is vm22 *. When the difference is equal to or more than the predetermined value Dmin, the value of vm12 * is used as the second voltage command value vm22 *. Furthermore, vm
22 * is compared with a value vm11 * adjacent in the direction of increasing the value. If the difference is small, the larger value vm11 * is changed so that the difference becomes Dmin, and the second voltage command value vm is changed.
21 *. When the difference is equal to or more than the predetermined value Dmin, v
The value of m11 * is directly used as the second voltage command value vm21 *.

Similarly, the second voltage command value vm24 is corrected so that the difference between the value vm14 * and the value adjacent thereto in the direction in which the value becomes smaller becomes a predetermined value Dmin or more.
*, Vm25 *, and vm26 * are set.

In the voltage command correction unit 11A, among the vm21 * to vm26 * set above, vu1a *, vv1a
*, Vw1a * are output to the PWM pulse generation unit 12A as the second voltage command values vu2a *, vv2a *, vw2a * in the first half of the PWM cycle, and the voltage command correction unit 11B outputs * Among them, vu1b
*, Vv1b *, vw1b *, and the second voltage command values vu2b *, vv2b *, in the first half of the PWM cycle.
Output to the PWM pulse generation unit 12B as vw2b *.

Then, in the latter half of the PWM cycle, the voltage command correction unit 11A executes vu1a *, vv1a *, vw1.
The phase voltage having a value offset to the opposite side by the same amount as the correction performed in the first half based on a * is output as a second voltage command value to the PWM pulse generation unit 12A, and the voltage command correction unit 11B outputs vu1b *, A phase voltage having a value offset to the opposite side by the same amount as the correction performed in the first half based on vv1b * and vw1b * is output to the PWM pulse generation unit 12B as a second voltage command value. Other configurations are the same as in the previous embodiment.

The present embodiment is configured as described above. Even when the PWM pulses are individually supplied to the two sets of motors 5A and 5B sharing the DC power supply 1, the voltage commands in both of them are provided in the first half of the PWM cycle. Since the PWM pulse is generated based on the second voltage command value corrected so that all the values are separated from each other by at least a predetermined value Dmin, a predetermined value is set between the switching in each of the three-phase bridge circuits 3A and 3B. , The DC bus current Is can be reliably detected during switching, and the phase currents iua, iva, iwa, and iub, iv of each phase can be detected.
b and iwb can be calculated.

In this embodiment, control of two sets of motors has been described. However, the present invention can be similarly applied to control of three or more sets of motors. Further, in each embodiment, the difference between the adjacent phase voltages in the first half of the PWM cycle is corrected to be the predetermined value Dmin. However, the present invention is not limited to this, and the difference between the adjacent phase voltages in the second half of the PWM cycle is the predetermined value Dmin. It is also possible to set the correction amount so that the second voltage command value is offset in the reverse direction by the correction amount in the first half.

[0042]

As described above, the present invention relates to a PWM inverter for motor control which feeds back a phase current from an inverter main circuit to a motor to a current control unit.
The pulse generation means sets the timing interval of the rise or fall of the PWM pulse between the phases to a predetermined value or more, and
Since the WM pulse is generated, the current corresponding to each phase of the DC bus of the inverter main circuit can be reliably detected by one current sensor, and the phase current can be calculated based on the DC bus current.

When the difference between the phases arranged in the order of the magnitude of the first voltage command value is smaller than the predetermined interval value, the PWM pulse generating means sets the first phase of the two phases having the smaller difference at every PWM cycle. At least one of the voltage command values is corrected to a second voltage command value having the same value and an average value and different values in the first half and the second half of the cycle, and the difference between the phases is determined by a predetermined interval value. A voltage command correction unit configured as described above and a PWM pulse generation unit that outputs a PWM pulse in accordance with the second voltage command value can be provided. And especially
The voltage command correction unit corrects at least one first voltage command value of at least one of the two phases having a small difference in the first half of the 1 PWM cycle by a predetermined value in a direction to enlarge the difference, and only corrects the predetermined value in the second half of the cycle. The one first voltage command value can be corrected in the reverse direction to be a second voltage command value.
As a result, the difference between the voltage command values between the phases is widened so that the phase currents of the DC bus can be identified and detected, and the average value of the voltage command values in one entire cycle maintains the same level as before correction.

In the first half of one PWM cycle, when the two phases having a small difference include the phase of the largest value of the first voltage command value, the largest value of the first voltage command value is set to the predetermined value. When the two phases having a small difference include the phase of the smallest value of the first voltage command value, a predetermined value is subtracted from the first voltage command value of the smallest value to correct the difference. This prevents a situation in which the second voltage command value obtained by the correction approaches a phase having a sufficient interval before the correction and the difference becomes smaller than the predetermined interval value.

If the difference between the three phases arranged in the order of the magnitude of the first voltage command value is smaller than the predetermined interval value between adjacent ones, the first phase of the two phases selected in the first half of the 1 PWM cycle is determined. Are corrected by a first predetermined value and a second predetermined value, respectively, so that three adjacent phases are set to a predetermined interval value, and only the first predetermined value and the second predetermined value are selected in the latter half of the cycle. By correcting the first voltage command values of the two phases in the opposite direction to obtain the second voltage command values, even when all of the three phases are smaller than the predetermined interval value, the second voltage command values are not changed. The DC bus current corresponding to each phase is reliably detected by widening the interval between the phases, and the phase current can be calculated.

At this time, in particular, the phase of the largest value and the smallest value of the first voltage command value is selected, and the first voltage command value of the largest value is set to the first voltage command value in the first half of one PWM cycle.
Is added, and the second predetermined value is subtracted from the first voltage command value of the smallest value to perform correction, thereby increasing the PWM pulse timing interval between the phases with a minimum correction amount. The phase current can be determined.

Further, a current controller, a voltage command corrector, a PWM pulse generator, and an inverter main circuit are provided for each of the two sets of motors, and each inverter main circuit is supplied with power from a DC power supply via a common DC bus. In the PWM inverter for motor control that feeds back the phase current of the motor to each current control unit, the voltage command correction units are adjacent to each other in six phases arranged in the order of the magnitude of the first voltage command values from both current control units. The first voltage command value is corrected by a predetermined value set for each phase so that the difference between the phases is equal to or more than a predetermined interval value, and the second voltage is corrected in the reverse direction by the predetermined value in the second half of the cycle. In this case, the DC bus current corresponding to each phase is reliably detected by one current sensor even when the number of motors is increased to two. There are the phase current can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a first embodiment of the present invention.

FIG. 2 is a flowchart illustrating a flow of generating a second voltage command value.

FIG. 3 is a flowchart showing a flow of generating a second voltage command value.

FIG. 4 is a waveform chart illustrating the operation of the embodiment.

FIG. 5 is a block diagram showing a second embodiment.

FIG. 6 is a waveform chart showing a conventional problem.

[Explanation of symbols]

 Reference Signs List 1 inverter main circuit 2 DC power supply 3, 3A, 3B three-phase bridge circuit 4 switching element 5, 5A, 5B motor 6 capacitor 8 DC bus 10, 10A, 10B current control unit 11, 11A, 11B voltage command correction unit 12, 12A , 12B PWM pulse generator 13 Current sensor 14, 16-phase current calculator

Claims (8)

[Claims] 1. A current control unit for outputting a three-phase first voltage command value by current control, a PWM pulse generating means for outputting a PWM pulse based on the first voltage command value,
A motor control PWM inverter that includes an inverter main circuit that drives the motor under the control of M pulses and feeds back the phase current of the motor to the current control unit.
A phase current calculation unit configured to calculate the phase current based on a detection value of the current sensor and a PWM pulse output from a PWM pulse generation unit, wherein the PWM pulse generation unit includes
A PWM inverter for motor control, wherein a PWM pulse is output with a timing interval of a rise or a fall of a PWM pulse between respective phases being set to a predetermined value or more. 2. The method according to claim 1, wherein the PWM pulse generation unit is configured to:
When the difference between the phases arranged in the order of the magnitude of the voltage command values is smaller than the predetermined interval value, at least one value of the first voltage command values of the two phases having the smaller difference is replaced by the value at each PWM cycle. And a second voltage command value that makes the average value the same and different between the first half and the second half of the cycle, and makes the difference between the phases equal to or more than a predetermined interval value.
That outputs a PWM pulse according to the voltage command value of
2. The motor control PWM inverter according to claim 1, further comprising an M pulse generator. 3. The voltage command correction unit corrects a first voltage command value of at least one of two phases having a small difference in a first half of a 1PWM cycle by a predetermined value in a direction in which the difference is enlarged. 3. The motor control PWM according to claim 2, wherein in the second half of the step, the one first voltage command value is corrected in the reverse direction by the predetermined value to obtain the second voltage command value. Inverter. 4. The correction in the first half of the 1 PWM cycle is performed when the two phases having a small difference include a phase having the largest value of the first voltage command value. And when the two phases having the smaller difference include the phase of the smallest value of the first voltage command value, the predetermined value is subtracted from the first voltage command value of the smallest value. 4. The PWM inverter for motor control according to claim 3, wherein: 5. The voltage command correction unit according to claim 1, wherein when the three phase differences arranged in the order of the magnitude of the first voltage command value are smaller than a predetermined interval value between adjacent ones, the voltage command correction unit selects the two in the first half of one PWM cycle. The first voltage command values of the three phases are corrected by a first predetermined value and a second predetermined value, respectively, so that adjacent three phases are set to a predetermined interval value. 2 selected by the predetermined value of 2
4. The motor control PWM inverter according to claim 3, wherein the first voltage command value of the three phases is corrected in the reverse direction to obtain the second voltage command value. 6. The two selected phases are the phase of the largest value and the smallest value of the first voltage command value, and
The correction in the first half of the WM cycle is obtained by adding the first predetermined value to the largest first voltage command value and subtracting the second predetermined value from the smallest first voltage command value. The PWM inverter for motor control according to claim 5, wherein 7. A current control unit for outputting three-phase first voltage command values by current control to two sets of motors,
A voltage command correction unit that corrects the voltage command value and outputs a second voltage command value, a PWM pulse generation unit that outputs a PWM pulse based on the second voltage command value, and a motor controlled by the PWM pulse. And a corresponding inverter main circuit for driving each motor.Each inverter main circuit is supplied with power from a DC power supply via a common DC bus, and feeds back a phase current of each motor to a corresponding current control unit for motor control. In the PWM inverter, a current sensor is provided on the DC bus, and a phase current calculation unit that calculates the phase current based on a detection value of the current sensor and a PWM pulse output from a PWM pulse generation unit is provided. Each of the voltage command correction units has a predetermined interval value between adjacent phases in six phases arranged in order of magnitude of the first voltage command values from both current control units. When there is a small difference, in the first half of the 1 PWM cycle, the first voltage command value corresponding to each of the voltage command correction units is set so that the difference between the six adjacent phases is equal to or greater than a predetermined interval value. In the second half of the cycle, the corrected first voltage command value is corrected in the reverse direction by a predetermined value set for each of the phases to obtain the second voltage command value. A PWM inverter for motor control, characterized in that: 8. The system according to claim 2, wherein the predetermined interval value is a voltage difference corresponding to a time required for the current sensor to detect a current of the DC bus.
Or a PWM inverter for motor control according to 7.