JP2016086586A - Grid-connected inverter device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an interconnection inverter device capable of detecting the presence/absence of a failure in an interconnection switch while achieving miniaturization and low cost.SOLUTION: An interconnection inverter device 1a includes an inverter 2, an interconnection switch 3, a controller 6a, a first voltage detector 7, a second voltage detector 20 and a voltage bias circuit 22A. The controller 6a determines whether or not a failure exists in the interconnection switch 3, using a voltage detected by the first voltage detector 7 and a voltage detected by the second voltage detector 20, under a state where the interconnection switch 3 is open before the operation of the inverter 2.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a grid-connected inverter device that links a DC power generation system using an external DC power source such as a solar cell and a fuel cell to a commercial power system.

  Two examples are shown as a grid interconnection inverter device used to link a DC power generation system using an external DC power supply to a commercial power grid. One is a grid-connected inverter device that can be switched between a grid-operated operation function with a commercial power system and a self-sustaining operation function with the commercial power system disconnected. This is referred to as a “first grid-connected inverter device”. The other is, as shown in Patent Document 1, AC power to a load connected between the grid-connected inverter device and the commercial power system is connected to the grid-connected inverter device and the commercial power system. This is a grid-connected inverter device that switches between the case of supplying by operation and the case of supplying only from a commercial power system. This is referred to as a “second grid interconnection inverter device”.

  The first grid-connected inverter device converts DC power generated by an external DC power source into AC power, supplies the converted AC power to a general AC load, and supplies surplus power at that time to the commercial power system. . In that case, when the AC power required for the general AC load is insufficient only by the DC power from the external DC power source, the interconnection operation is performed to cover the commercial power system. When the commercial power system fails due to an accident or disaster, the commercial power system is disconnected, and if the DC power from the external DC power supply is sufficient, the converted AC power is supplied to the general AC load for operation. It is now possible to carry out self-sustaining operation.

  In a grid-connected inverter device that can be implemented by switching between a grid-operated operation function with such a commercial power system and a self-sustained operation function that separates the commercial power system, an interconnection switch, a self-sustained switch, Are connected in parallel, a commercial power system is connected via a connection switch, and a general AC load is connected via a self-contained switch. That is, in the interconnected operation mode, control is performed so that the interconnected switch is closed and the independent switch is opened, and in the independent operation mode, the independent switch is closed and the interconnected switch is opened. When the independent operation mode is performed when the interconnection switch has failed in welding, the autonomous operation output flows out to the commercial power system via the interconnection switch in which welding failure has occurred. It has been practiced to have a two-stage serial configuration.

  Also in the second grid-connected inverter device disclosed in Patent Document 1, a two-stage series-connected switch is interposed between the output terminal of the inverter unit and the commercial power system, so that one unit is connected. A configuration for dealing with a case where a system switch fails in welding is shown. In Patent Document 1, the interconnection switch is referred to as “disconnection switch”.

JP 2004-187362 A

  However, since the size of each interconnection switch is large, if the interconnection switches are in a two-stage series configuration, any grid-connected inverter device with a capacity of 4 kW that is linked to an AC 200 volt commercial power system can be used. A current capacity of 20 amperes or more is required. Therefore, there is a problem that a large space is required and the cost is increased.

  Further, in the second grid-connected inverter device, there is a problem that the grid-connected inverter device may start operation when two linked switches are welded at the same time. Therefore, in Patent Document 1, one interconnected switch connected between the inverter unit and the commercial power system, a control unit that controls the output of the inverter unit, and the inverter unit side of the interconnected switch Between the terminals detected by the voltage detector in a state immediately before starting the interconnection operation in which the control unit stops the inverter operation and turns off the interconnection switch. A grid-connected inverter device that determines whether a grid-connected switch is normal based on a voltage has been proposed.

  However, in the technique described in Patent Document 1, since the presence or absence of abnormality of the interconnection switch is detected by comparing the voltage or frequency detected by the voltage detector, the two connections constituting the interconnection switch are detected. When either one of the pieces is welded, there is a problem that an abnormality may not be detected. In addition, when the commercial power system is in a power failure state, the voltage detected by the voltage detectors placed before and after the interconnection switch is zero regardless of whether the interconnection switch is welded or not. There is also a problem that the presence or absence of welding of the interconnection switch cannot be detected.

  The present invention has been made in view of the above, and an object of the present invention is to obtain a grid-connected inverter device capable of detecting the presence or absence of an abnormality in the grid-connected switch while achieving downsizing and cost reduction.

  In order to solve the above-described problems and achieve the object, the present invention includes an inverter unit that converts DC power into AC power, an interconnection switch installed between the inverter unit and the commercial power system, A control unit for controlling the inverter unit and the interconnection switch, a first voltage detection unit for detecting a voltage at both ends of the interconnection switch on the inverter unit side, and a commercial power system of the interconnection switch A second voltage detection unit that detects a voltage at both ends of the connection side, and a voltage bias circuit that is connected to both ends of the interconnection switch on the inverter unit side and applies a bias voltage, and the control unit includes: Using the voltage detected by the first voltage detection unit and the voltage detected by the second voltage detection unit in a state where the interconnection switch is opened before the operation of the inverter unit, Whether there is an abnormality in the interconnection switch Characterized in that it constant.

  According to the present invention, there is an effect that it is possible to detect the presence / absence of an abnormality in the interconnection switch while achieving size reduction and cost reduction.

The block diagram which shows the principal part structure of the grid connection inverter apparatus which concerns on Embodiment 1 of this invention. First configuration diagram of a voltage bias circuit according to the first embodiment of the present invention Second configuration diagram of the voltage bias circuit according to the first embodiment of the present invention. The flowchart for determining the presence or absence of abnormality of the interconnection switch which concerns on Embodiment 1 of this invention The block diagram which shows the principal part structure of the grid connection inverter apparatus which concerns on Embodiment 2 of this invention. The flowchart for determining the presence or absence of the abnormality of the interconnection switch which concerns on Embodiment 2 of this invention The block diagram which shows the principal part structure of the grid connection inverter apparatus which concerns on Embodiment 3 of this invention. The block diagram which shows the example which changed the connection position of the voltage bias circuit which concerns on Embodiment 5 of this invention Block diagram showing a configuration of a voltage bias circuit according to a sixth embodiment of the present invention

  Below, the grid connection inverter apparatus which concerns on embodiment of this invention is demonstrated in detail based on drawing. Note that the present invention is not limited to the embodiments.

Embodiment 1 FIG.
FIG. 1 is a block diagram showing a main configuration of a grid-connected inverter device 1a according to Embodiment 1 of the present invention. FIG. 1 shows a configuration example of the grid interconnection inverter device 1a used in the photovoltaic power generation system, and this is the same in the second, third, and fourth embodiments described later. Further, FIG. 1 shows a grid-connected inverter device 1a that can be switched between a grid-operated operation function with the commercial power system 26 and a self-sustaining operation function with the commercial power system 26 disconnected. This also applies to Embodiments 2, 3, and 4 described later.

  A grid-connected inverter device 1 a shown in FIG. 1 includes an inverter unit 2, a single interconnection switch 3 connected to the AC output terminal of the inverter unit 2, and a self-supporting unit connected to the AC output terminal of the inverter unit 2. A switch 4, a self-supporting output terminal 5 connected to the self-supporting switch 4, a control unit 6 a, a first voltage detection unit 7, and a second voltage detection unit 20 are provided.

  The inverter unit 2 includes a converter circuit 2a, an inverter circuit 2b, and a filter circuit 2c. The converter circuit 2a includes a capacitor 11, a reactor 12, a switching element 13, and an output diode 14. In the illustrated example, these elements are arranged to constitute a booster circuit. That is, the capacitor 11 is arranged in parallel connection between the positive and negative output terminals of the solar cell 25 that is an external DC power supply. One end of the reactor 12 is connected to the positive electrode end of the capacitor 11, and the other end of the reactor 12 is connected to one end of the switching element 13 and the connection end of the output diode 14. The cathode of the output diode 14 is connected to the positive bus P as the positive output terminal of the converter circuit 2a. The negative output terminal of the converter circuit 2 a is connected to the negative bus Q together with the negative terminal of the capacitor 11 and the other end of the switching element 13.

  The inverter circuit 2b includes a capacitor 15 and two arms 17a and 17b. The capacitor 15 is connected between the positive bus P and the negative bus Q so as to constitute the input terminal of the inverter circuit 2b. The arm 17a includes switching elements 16a and 16b connected in series between the positive electrode bus P and the negative electrode bus Q, and the arm 17b is a switching device connected in series between the positive electrode bus P and the negative electrode bus Q. It consists of elements 16c and 16d. In FIG. 1, a series circuit of a switching element 16a that is an upper-end positive-side switching element and a switching element 16b that is a lower-end negative-side switching element is an arm 17a, and a switching element 16c that is an upper-end positive-side switching element and a lower-end negative-side switching element A series circuit with the switching element 16d is an arm 17b. A connection end between the switching element 16a and the switching element 16b and a connection end between the switching element 16c and the switching element 16d each constitute an output end of the inverter circuit 2b.

  Filter circuit 2c has one end connected to reactor 18a connected to one output end of inverter circuit 2b, one end connected to reactor 18b connected to the other output end of inverter circuit 2b, and one end connected to the other end of reactor 18a. The other end of the capacitor 18 is connected to the other end of the reactor 18b. The other end of the reactor 18a and the other end of the reactor 18b are AC output ends of the inverter unit 2, and the interconnection switch 3 and the independent switch 4 are connected in parallel to the AC output end.

  In the converter circuit 2a of the inverter unit 2 configured as described above, the DC voltage generated by the solar battery 25 is boosted to a DC voltage necessary for the operation of the inverter circuit 2b, and is output from the converter circuit 2a in the inverter circuit 2b. The DC voltage is smoothed and held as a bus voltage by the capacitor 15. The bus voltage is converted into an AC voltage by the on / off operation of the switching elements 16a, 16b, 16c, and 16d that constitute the two arms 17a and 17b. The filter circuit 2c shapes and smoothes the AC voltage pulse-width modulated by the inverter circuit 2b into an AC voltage having a sine wave-like smooth AC waveform. The AC voltage is applied to one end of the contact pieces 3 a and 3 b of the interconnection switch 3 and to one end of the contact pieces 4 a and 4 b of the self-standing switch 4.

  One end of the contact piece 3a of the interconnection switch 3 is connected to the other end of the reactor 18a of the filter circuit 2c, and one end of the contact piece 3b of the interconnection switch 3 is connected to the other end of the reactor 18b of the filter circuit 2c. Is done. A commercial power system 26 is connected to the other end of the contact piece 3a of the interconnection switch 3 and the other end of the contact piece 3b. The interconnection switch 3 according to the first embodiment is not a two-stage series configuration in which another AC switch (not shown) is connected in series to one interconnection switch 3, but only by one interconnection switch 3. It has a one-stage configuration.

  One end of the contact piece 4a of the self-standing switch 4 is connected to the other end of the reactor 18a of the filter circuit 2c, and one end of the contact piece 4b of the self-standing switch 4 is connected to the other end of the reactor 18b of the filter circuit 2c. . A self-supporting output end 5 is connected to the other end of the contact piece 4a of the self-standing switch 4 and the other end of the contact piece 4b.

  The independent output terminal 5 is an outlet into which a power cord plug of a general electric device used in a home or factory is inserted, and is provided in the system interconnection inverter device according to the present invention.

  In FIG. 1, one AC output end of the inverter unit 2, that is, the other end of the reactor 18 a is expressed as R, the other AC output end of the inverter unit 2, that is, the other end of the reactor 18 b is expressed as S, and commercial power A system connection line that connects one end of the system 26 to the other end of the contact piece 3 a of the interconnection switch 3 is denoted as T, and the other end of the commercial power system 26 is the other end of the connection piece 3 b of the interconnection switch 3. A system connection line to be connected to is denoted by U.

  The first voltage detection unit 7 detects the voltage between the other end R of the reactor 18a and the other end S of the reactor 18b, that is, the output voltage of the inverter unit 2, and outputs the detected voltage to the control unit 6a. The second voltage detection unit 20 detects a voltage between the system connection line T and the system connection line U, and outputs the detected voltage to the control unit 6a.

  The voltage bias circuit 22A is connected between the other end R of the reactor 18a and the other end S of the reactor 18b, and generates a voltage between the RSs. When the inverter circuit 2b is stopped, the voltage bias circuit 22A generates a voltage between the RSs. On the other hand, when the inverter circuit 2b is operating, the output of the inverter circuit 2b is dominant with respect to the voltage between the RSs, so the output of the voltage bias circuit 22A is ignored.

  The controller 6a causes the switching element 13 to perform a switching operation so that the converter circuit 2a performs a boost operation. Further, the control unit 6a causes the switching elements 16a, 16b, 16c, and 16d constituting the two arms 17a and 17b of the inverter circuit 2b to perform a switching operation for converting DC power output from the converter circuit 2a into AC power. . Then, the control unit 6a performs control to supply the converted AC power to the commercial power system 26 by closing the interconnection switch 3 to open the independent switch 4 in the interconnection operation mode. Moreover, the control part 6a carries out control which supplies the converted alternating current power to the general electric equipment from the independent output terminal 5 by closing control of the independent switch 4 and opening control of the interconnection switch 3 at the time of the independent operation mode. Do.

  The grid-connected inverter device 1a configured in this way converts the DC power generated by the solar battery 25 into AC power, and supplies the converted AC power to the commercial power system 26. A function is provided that can be implemented by switching the self-sustained operation mode supplied from the self-sustained output end 5 to various electric devices that are loads not shown. However, since this operation is publicly known, detailed description is omitted in the first embodiment. The feature of the present invention is that safety can be ensured and the size and cost can be reduced even if the interconnection switch 3 has a single-stage configuration and the interconnection switch 3 has a single-stage configuration. . Hereinafter, the structure which concerns on the characteristic part of this invention is demonstrated.

  In FIG. 1, before starting the operation of the inverter unit 2, the control unit 6a is based on the voltage detected by the first voltage detection unit 7 and the voltage detected by the second voltage detection unit 20. The presence or absence of abnormality of the switch 3 is determined. When it is determined that the switch 3 is normal, the operation of the inverter unit 2 is started, and the operation shifts to the interconnection operation control with the commercial power system 26. On the other hand, when it determines with abnormality having arisen in the interconnection switch 3, the control part 6a displays the fact that abnormality has occurred in the interconnection switch 3 on the display which is not illustrated, without starting an operation | movement.

  Next, the role of the voltage bias circuit 22A will be specifically described.

  FIG. 2 is a first configuration diagram of the voltage bias circuit 22A according to the first embodiment of the present invention, and FIG. 3 is a second configuration diagram of the voltage bias circuit 22A according to the first embodiment of the present invention. As shown in FIG. 2, the voltage bias circuit 22A has a configuration in which a voltage source 22a and a resistor 22b are connected in series. The voltage source 22a is connected between the other end R of the reactor 18a and the other end S of the reactor 18b, and generates a constant voltage at the RS end. The resistor 22b limits the current that flows to the voltage source 22a when the interconnection switch 3 has a short circuit failure, and prevents the failure of the voltage source 22a. The voltage between the RSs is determined by the voltage drop between the voltage source 22a and the resistor 22b. However, since a leakage current flows through the switching elements 16a, 16b, 16c, and 16d, the current flowing through the resistor 22b is changed to the switching elements 16a, 16b, 16c, and so on. The voltage between RSs cannot be kept constant unless it is sufficiently larger than the leakage current of 16d. This is because when the amount of leakage current changes due to a change in bus voltage between the positive bus P and the negative bus Q, the value of the current flowing through the resistor 22b changes. The resistor 22b is preferably a circuit having an impedance in which a flowing current is 1 milliampere or less in consideration of safety.

  When the switching elements 16a, 16b, 16c, and 16d of the inverter circuit 2b are stopped, when the contact piece 3a and the contact piece 3b of the interconnection switch 3 are normal, the first voltage detection unit 7 detects them. Is equal to the bias voltage generated by the voltage source 22a of the voltage bias circuit 22A. On the other hand, when the contact piece 3a and the contact piece 3b of the interconnection switch 3 have a welding failure, the voltage detected by the first voltage detector 7 is between the system connection line T and the system connection line U. Since it becomes equal to a voltage, it can be determined whether abnormality has arisen in the interconnection switch 3. FIG. That is, when the contact piece 3a and the contact piece 3b of the interconnection switch 3 are welded and the commercial power system 26 is normal, the voltage detected by the first voltage detector 7 and the second voltage detector The system voltage that is the voltage detected at 20 becomes equal. When the contact piece 3a and the contact piece 3b of the interconnection switch 3 are welded and the commercial power system 26 is out of power, the voltage detected by the first voltage detection unit 7 and the second voltage detection unit 20 The detected bias voltage is equal to the bias voltage generated by the voltage source 22a of the voltage bias circuit 22A. Thereby, in the control part 6a, it can be determined whether abnormality has arisen in the interconnection switch 3. FIG. Note that, in determining whether the voltage detected by the first voltage detector 7 and the voltage detected by the second voltage detector 20 are equal to the bias voltage, it is generated by the voltage source 22a of the voltage bias circuit 22A. A voltage detector for detecting the bias voltage is provided. In the control unit 6a, the voltage detected by the voltage detector is detected by the first voltage detection unit 7 and the second voltage detection unit 20. It may be configured to determine whether or not the voltage is equal, or a voltage value corresponding to a bias voltage generated by the voltage source 22a of the voltage bias circuit 22A is set in the control unit 6a in advance, and the control unit 6a sets this voltage value. May be configured to determine whether or not the voltage detected by the first voltage detector 7 is equal to the voltage detected by the second voltage detector 20. In this embodiment, the latter configuration is used.

  In addition, when the connection piece 3a and the connection piece 3b of the interconnection switch 3 have a welding failure, if the system connection line T and the system connection line U are short-circuited for some reason, the first voltage The voltage detected by the detector 7 and the voltage detected by the second voltage detector 20 are equal to zero volts. Therefore, even when the connection between the system connection line T and the system connection line U is short-circuited, the control unit 6a can determine whether or not an abnormality has occurred in the interconnection switch 3. The effect is the same regardless of whether the voltage source 22a described in the first embodiment is a DC voltage source or an AC voltage source, and the configuration is not limited.

  Note that the voltage between the grid connection line T and the grid connection line U is an AC voltage, and varies depending on the state of the commercial power system 26. Therefore, when the voltage source 22a constituting the voltage bias circuit 22A is an AC voltage source, the first voltage detection unit 7 detects when the contact piece 3a and the contact piece 3b of the interconnection switch 3 have a welding failure. There is a possibility that it is not possible to distinguish between the voltage output from the voltage bias circuit 22A and the voltage between the system connection line T and the system connection line U. On the other hand, when the voltage source 22a is a DC power supply, whether the voltage detected by the first voltage detector 7 is a voltage output from the voltage bias circuit 22A, the system connection line T, the system connection line U, And the abnormality detection accuracy of the interconnection switch 3 is increased. Therefore, in the first embodiment, as shown in FIG. 3, the voltage source 22a of the voltage bias circuit 22A is a DC voltage source.

  FIG. 4 is a flowchart for determining whether or not there is an abnormality in the interconnection switch 3 according to Embodiment 1 of the present invention.

  First, the control unit 6a controls the switching elements 16a, 16b, 16c, and 16d of the converter circuit 2a and the inverter circuit 2b to be in an off state, and opens the interconnection switch 3 (step S1).

  Next, control unit 6a drives switching element 13 of converter circuit 2a to boost the bus voltage between positive bus P and negative bus Q of inverter unit 2 (step S2). In the first embodiment, a method of boosting the bus voltage to 300 volts is adopted. The voltage value of the bus voltage to be boosted is an example, and can be set to a different value depending on the embodiment. The reason why the bus voltage is boosted is that the abnormality detection accuracy is increased by increasing the bus voltage, and the abnormality can be detected without increasing the bus voltage.

Next, the control unit 6a monitors the voltage detected by the first voltage detection unit 7 and the voltage detected by the second voltage detection unit 20 in a state where the bus voltage is 300 volts. From the voltage detected by the voltage detector 7 and the voltage detected by the second voltage detector 20, the AC components V _RSAC and V _TUAC and the DC components V _RSDC and V _TUDC are extracted ( Step S3).

When the voltage detected by the first voltage detector 7 and the voltage detected by the second voltage detector 20 are divided into an AC component and a DC component, the offset of the DC component of the detector affects. Therefore, when configuring the first voltage detection unit 7 and the second voltage detection unit 20, it is desirable to remove the DC component offset in advance. Each AC component and DC component of the voltage detected by the first voltage detection unit 7 and the voltage detected by the second voltage detection unit 20 are calculated as follows. However, V _RS is the value of the voltage detected by the first voltage detector 7, V _RSRMS is the effective value of the voltage detected by the first voltage detector 7, and V _TU is the second voltage detector 20. The value of the detected voltage, V _TURMS represents the effective value of the voltage detected by the second voltage detection unit 20, and T represents the average value or effective value calculation period.
V _RSDC = (ΣV _RS ) / T
V _RSRMS = √ (Σ (V _RS * V _RS ) / T)
V _RSAC = √ (V _RSRMS * V _RSRMS− V _RSDC * V _RSDC )
V _TUDC = (ΣV _TU ) / T
V _TURMS = √ (Σ (V _TU * V _TU ) / T)
V _TUAC = √ (V _TURMS * V _TURMS -V _TUDC * V _TUDC )

Next, the control unit 6a is connected based on the AC component and DC component of the voltage detected by the first voltage detection unit 7 and the voltage detected by the second voltage detection unit 20 calculated above. It is determined whether or not an abnormality has occurred in both the contact pieces 3a and 3b of the system switch 3 (step S4). When the interconnection switch 3 is normal, the AC and DC components are ideally as follows.
V _RSAC, V _TUDC = 0 volts V _RSDC ≥ α

V _{RSAC and} V _TUDC do not become 0 volts due to variations in the parts constituting the first voltage detection unit 7 and the second voltage detection unit 20. Therefore, in the first embodiment, V _{RSAC and} V _TUDC ≦ 5 volts are determined as determination values. In addition, α, which is a determination criterion for V _RSDC , is a value determined by the voltage source 22a and the resistor 22b constituting the voltage bias circuit 22A. In the first embodiment, α = 7 volts. This is not the case. Note that V _TUAC is not used for determination because V _TUAC cannot determine whether the interconnection switch 3 is normal or abnormal.

  In this way, the control unit 6a determines whether or not an abnormality has occurred in the interconnection switch 3 based on the determination value (step S5). When an abnormality occurs in the interconnection switch 3 (step S5, Yes), the control unit 6a stops the transition to the operation start (step S6), and shows that an abnormality occurs in the interconnection switch 3. Do not display on the display. When there is no abnormality in the interconnection switch 3 (step S5, No), the controller 6a shifts to the start of operation (step S7). In addition, when detecting the voltage of each voltage detection part, since the charging element called a capacitor | condenser exists on a structure, it is desirable for the control part 6a to perform abnormality determination of the interconnection switch 3 in the stable state.

  As described above, according to the grid-connected inverter device 1a of the first embodiment, before the operation of the inverter unit 2, the presence / absence of a short circuit failure of the grid switch 3, that is, the presence / absence of an abnormality of the grid switch 3 is detected. be able to. Therefore, in order to ensure safety, there is no need to add an AC switch in addition to the interconnection switch 3 between the inverter unit 2 and the commercial power system 26, and a single interconnection switch 3 is installed. However, safety can be ensured, and at the same time, miniaturization and cost reduction can be achieved. Further, in the grid-connected inverter device 1a according to the first embodiment, since it is not necessary to add an AC switch in addition to the link switch 3, the volume of parts can be reduced and LCA (Life Cycle Assessment) can be achieved. From the point of view, a preferable device can be provided.

Embodiment 2. FIG.
FIG. 5 is a block diagram showing a main configuration of a grid-connected inverter device 1b according to Embodiment 2 of the present invention. In FIG. 5, the same or equivalent components as those shown in FIG. Here, the description will focus on the parts related to the second embodiment. In the grid interconnection inverter device 1b according to the second embodiment, a third voltage detection unit 9 and a fourth voltage detection unit 21 are added in addition to the configuration shown in FIG. A control unit 6b is provided instead of the control unit 6a. Other configurations are the same as those of the grid interconnection inverter device 1a according to the first embodiment.

  The third voltage detector 9 detects the voltage of the system connection line U with respect to the negative electrode bus Q, and outputs the detected voltage to the controller 6b. The fourth voltage detection unit 21 detects the voltage of the negative electrode bus Q with respect to the positive electrode bus P, and outputs the detected voltage to the control unit 6b. The control unit 6b detects the voltage of the system connection line T with respect to the negative electrode bus Q by adding the voltage detected by the third voltage detection unit 9 to the voltage detected by the second voltage detection unit 20. be able to.

  FIG. 6 is a flowchart for determining whether or not there is an abnormality in the interconnection switch 3 according to Embodiment 2 of the present invention.

  The operation from step S1 to step S6 in FIG. 6 is the same as the operation from step S1 to step S6 in the first embodiment. That is, before the operation of the inverter unit 2, the control unit 6b drives the switching element 13 of the converter circuit 2a in a state in which the interconnection switch 3 is opened, boosts the bus voltage of the inverter unit 2, and the first When the voltage of the voltage detection unit 7 and the second voltage detection unit 20 detects a voltage value at which it can be determined that both the contact pieces 3a and 3b of the interconnection switch 3 are welded, the interconnection switch 3 Therefore, the shift to the operation start is stopped, and the fact that an abnormality has occurred in the interconnection switch 3 is displayed on a display (not shown).

  When no abnormality has occurred in the interconnection switch 3 (step S5, No), the control unit 6b determines whether or not an abnormality has occurred in the contact piece on one side of the interconnection switch 3 (step S7). This will be specifically described below. The controller 6b controls the switching element 13 of the converter circuit 2a and the switching elements 16a, 16b, 16c, and 16d of the inverter circuit 2b so that the duty ratio is 50%. At this time, the voltage at the other end R of the reactor 18 a with respect to the negative electrode bus Q is ½ of the bus voltage between the positive electrode bus P and the negative electrode bus Q. Similarly, the voltage at the other end S of the reactor 18 b with respect to the negative electrode bus Q is ½ of the bus voltage between the positive electrode bus P and the negative electrode bus Q. Note that the voltage at the other end R of the reactor 18a with respect to the negative electrode bus Q and the voltage at the other end S of the reactor 18b with respect to the negative electrode bus Q are the duty ratio of each switching element 16a, 16b, 16c, 16d of the inverter circuit 2b, and the positive electrode. It is determined by multiplying the bus voltage between the bus P and the negative bus Q. In the second embodiment, each of the switching elements 16a, 16b, 16c, and 16d of the inverter circuit 2b has a duty ratio of 50%. This is between the other end R of the reactor 18a and the other end S of the reactor 18b. Since no voltage is accumulated in the capacitor 19 constituting the filter circuit 2c, there is no waiting time for discharging the capacitor 19 when the interconnection switch 3c is normal, and the operation starts smoothly. This is because the duty ratio is not limited to this value.

  At this time, if the contact piece 3b of the interconnection switch 3 is welded and is in a conductive state, the voltage of the system connection line U with respect to the negative electrode bus Q detected by the third voltage detection unit 9 is the fourth voltage detection. It becomes half of the bus voltage between the positive electrode bus P and the negative electrode bus Q detected by the section 21, and it can be detected that an abnormality has occurred in the contact piece 3b. When the contact piece 3b is normal, the negative electrode bus Q and the system connection line U are disconnected from the other end S of the reactor 18b by the contact piece 3b of the interconnection switch 3. Therefore, it goes without saying that the voltage of the system connection line U with respect to the negative electrode bus Q is indefinite.

  Similarly, if the contact piece 3a of the interconnection switch 3 is welded and is in a conductive state, the voltage of the system connection line T with respect to the negative electrode bus Q is detected by the second voltage detection unit 20 and the third voltage detection unit 9. Since the detected voltage is half of the bus voltage between the positive bus P and the negative bus Q, the control unit 6b can detect that an abnormality has occurred in the contact piece 3a. . When the contact piece 3a is normal, the voltage of the system connection line T with respect to the negative electrode bus Q becomes indefinite as in the case where the contact piece 3b is normal.

  Thus, the control part 6b determines whether abnormality has arisen in the contact piece 3a or the contact piece 3b of the interconnection switch 3 (step S7). When an abnormality has occurred in the contact piece 3a or the contact piece 3b of the interconnection switch 3 (step S8, Yes), the control unit 6b stops the transition to the start of operation (step S6), and the interconnection switch 3 The fact that an abnormality has occurred is displayed on a display (not shown). When there is no abnormality in the contact piece 3a or the contact piece 3b of the interconnection switch 3 (No at Step S8), the control unit 6b shifts to the start of operation (Step S9).

  In the second embodiment, the third voltage detection unit 9 is provided in order to detect the voltage of the system connection line U with respect to the negative electrode bus Q. However, the voltage detection unit that detects the voltage of the system connection line T with respect to the negative electrode bus Q is provided. The same effect can be obtained even if the is provided. Moreover, since the voltage of the inverter part 2 should just be measured, you may detect the voltage with respect to the positive electrode bus P instead of the negative electrode bus Q.

  As described above, according to the second embodiment, before the inverter unit 2 is operated, there is a short circuit failure in the interconnection switch 3 and each contact piece 3a, 3b, that is, the interconnection switch 3 and each contact piece 3a, 3b. The presence or absence of an abnormality can be detected. The abnormality detection operation of the interconnection switch 3 and the contact pieces 3a and 3b can be performed regardless of whether the commercial power system 26 is in an energized state or a power failure state. Therefore, in order to ensure safety, there is no need to add an AC switch in addition to the interconnection switch 3 between the inverter unit 2 and the commercial power system 26, and a single interconnection switch 3 is installed. In addition, safety can be ensured, and the grid-connected inverter device 1b can be reduced in size and cost.

Embodiment 3 FIG.
FIG. 7 is a block diagram showing a main configuration of a grid-connected inverter device 1c according to Embodiment 3 of the present invention. In FIG. 7, the same or equivalent components as those shown in FIG. Here, the description will be focused on the portion related to the third embodiment.

  The grid-connected inverter device 1c according to the third embodiment is configured to be linked to the single-phase three-wire system 27. The single-phase three-wire system 27 is shown in a configuration in which two single-phase systems 27a and 27b are connected in series, and is connected to one end of a series circuit of the single-phase systems 27a and 27b, that is, connected to the single-phase system 27a side. Line T, system connection line U connected to the other end of the series circuit of single-phase systems 27a and 27b, that is, the single-phase system 27b side, and system connection line O connected to the connection end of single-phase systems 27a and 27b Has three lines. In the grid-connected inverter device 1c linked to the single-phase three-wire system 27, the single-phase system that is one end of the series circuit of the single-phase systems 27a and 27b through the system connection line T to the contact piece 3a of the grid switch 3 27a side is connected. In the grid-connected inverter device 1c, the single-phase system 27b side that is the other end of the series circuit of the single-phase systems 27a and 27b is connected to the contact piece 3b of the grid switch 3 through the system connection line U.

  In the grid interconnection inverter device 1c according to the third embodiment, the first voltage detection unit 7, the third voltage detection unit 9, and the fourth voltage detection unit 21 detect the voltage as in the second embodiment. However, the second voltage detection unit 20 is divided into two voltage detection units 20a and 20b, and a control unit 6c is provided instead of the control unit 6b shown in FIG.

  The voltage detection unit 20a detects a voltage between the system connection line T and the system connection line O connected to the connection ends of the single-phase systems 27a and 27b, and outputs the detected voltage to the control unit 6c. The voltage detection unit 20b detects a voltage between the system connection line U and the system connection line O, and outputs the detected voltage to the control unit 6c.

  The controller 6c adds up the voltages detected by the voltage detectors 20a and 20b. Thereby, in the control part 6c, the voltage equal to the voltage detected by the 2nd voltage detection part 20 shown in FIG. 5 can be obtained. Therefore, the control part 6c can detect the presence or absence of abnormality of the interconnection switch 3 and each contact piece 3a, 3b before the operation of the inverter part 2 is started in the same procedure as in the second embodiment.

Embodiment 4 FIG.
In the fourth embodiment, in the configuration shown in FIG. 1, FIG. 5 and FIG. 7, an example in which the presence or absence of abnormality in the contact pieces 3a and 3b of the interconnection switch 3 is determined by changing the operation of the inverter circuit 2b. Show. Here, a description will be given with reference to FIG.

  In FIG. 5, the control unit 6 b keeps the interconnection switch 3 in the open circuit state before the inverter unit 2 starts operation. The control unit 6b drives the switching element 13 of the converter circuit 2a with the interconnection switch 3 opened, boosts the bus voltage of the inverter unit 2, and the first voltage detection unit 7 and the second voltage detection. When the voltage of the unit 20 detects a voltage value at which it is possible to determine that both of the two contact pieces 3a and 3b of the interconnection switch 3 are welded, it is determined that an abnormality has occurred in the interconnection switch 3. To cancel the transition to the start of operation. Moreover, when the control part 6b detects the voltage which can be judged that both the two contact pieces 3a and 3b of the interconnection switch 3 are not welded, operation | movement of the arms 17a and 17b which comprise the inverter circuit 2b Are controlled as in the following (1) and (2).

  (1) In the control unit 6b, one arm 17a that constitutes the inverter circuit 2b has a DC voltage that is a half of the bus voltage between the positive bus P and the negative bus Q of the inverter circuit 2b as a specific value. The switching element 13 of the converter circuit 2a and the switching elements 16a and 16b constituting the arm 17a of the inverter circuit 2b are controlled so as to be output as the above voltage. The voltage having a specific value is a voltage that can be output by the inverter circuit 2b. On the other hand, the control unit 6b controls the switching elements 16c and 16d of the other arm 17b constituting the inverter circuit 2b to be in an off state. Then, the voltage with respect to the negative electrode bus Q at the other end R of the reactor 18a is ½ of the bus voltage between the positive electrode bus P and the negative electrode bus Q, and the voltage with respect to the negative electrode bus Q at the other end S of the reactor 18b is indefinite. It becomes. In this case, if the contact piece 3a of the interconnection switch 3 is welded and is in a conductive state, the system for the negative electrode bus Q detected from the outputs of the second voltage detection unit 20 and the third voltage detection unit 9 The voltage of the connection line T is a half of the bus voltage between the positive bus P and the negative bus Q. Therefore, the control part 6b can detect abnormality of the contact piece 3a. Even if the contact piece 3b is also welded at this time, the other arm 17b of the inverter circuit 2b is turned off, so that the filter circuit 2c, the contact piece 3a of the interconnection switch 3 from the arm 17a of the inverter circuit 2b, commercial An excessive current does not flow through the power system 26, the contact piece 3b of the interconnection switch 3, and the circuit that reaches the arm 17b of the inverter circuit 2b via the filter circuit 2c.

  (2) The control unit 6b is configured such that the other arm 17b constituting the inverter circuit 2b generates a DC voltage that is a half of the bus voltage between the positive bus P and the negative bus Q of the inverter circuit 2b with a specific value. The switching element 13 of the converter circuit 2a and the switching elements 16c and 16d constituting the arm 17b of the inverter circuit 2b are controlled so as to be output as the above voltage. The voltage having a specific value is a voltage that can be output by the inverter circuit 2b. On the other hand, the control unit 6b controls the switching elements 16a and 16b of one arm 17a constituting the inverter circuit 2b to be in an off state. Then, the voltage with respect to the negative electrode bus Q at the other end S of the reactor 18b is ½ of the bus voltage between the positive electrode bus P and the negative electrode bus Q, and the voltage with respect to the negative electrode bus Q at the other end R of the reactor 18a is indefinite. It becomes. In this case, if the contact piece 3b of the interconnection switch 3 is welded and is in a conductive state, the voltage of the system connection line U with respect to the negative bus Q detected by the output of the third voltage detector 9 is positive bus This is one half of the bus voltage between P and the negative electrode bus Q. Therefore, the control part 6b can detect abnormality of the contact piece 3b. Even if the contact piece 3a is also welded at this time, one arm 17a of the inverter circuit 2b is turned off, so that the filter circuit 2c, the contact piece 3b of the interconnection switch 3 from the arm 17b of the inverter circuit 2b, commercial Excessive current does not flow through the power system 26, the contact 3a of the interconnection switch 3, and the circuit reaching the arm 17a of the inverter circuit 2b via the filter circuit 2c.

  In the first, second, third, and fourth embodiments, the case where the switching circuit of the inverter circuit 2b is configured by two arms has been described. In the case of three arms, it goes without saying that one arm is controlled to be in the OFF state, and the above-described operation control (1) and (2) is performed using the remaining two arms.

  As described above, according to the fourth embodiment, before starting the operation of the inverter unit 2, one of the two arms of the inverter circuit 2b in the inverter unit 2 outputs a voltage having a specific value. By operating the other arm in the OFF state, it is possible to detect the presence / absence of an abnormality in each contact piece 3a, 3b of the interconnection switch 3. This abnormality detection operation can be performed similarly regardless of whether the commercial power system is in an energized state or a power failure state. When all the contact pieces 3a and 3b of the interconnection switch 3 are in a short circuit state, even if the inverter circuit 2b is operated, the arm on one side is turned off, so that there is no possibility that an excessive current flows. .

  In the above description, a solar cell power generation system is shown as a DC power generation system. However, the grid interconnection inverter device according to the present invention is similarly applied to a grid interconnection inverter device used in a fuel cell power generation system. Needless to say, you can. In the above description, an example in which a DC voltage is output as a voltage having a specific value output from the inverter unit 2 in order to detect an abnormality in the interconnection switch 3 has been described. Can be obtained.

Embodiment 5 FIG.
FIG. 8 is a block diagram showing an example in which the connection position of the voltage bias circuit 22A according to the fifth embodiment of the present invention is changed. The fifth embodiment shows an example in which the connection position of the voltage bias circuit 22A is changed in the configuration shown in FIG. 1, FIG. 5, and FIG. As shown in FIG. 8, the voltage bias circuit 22A is connected in parallel to the output terminals of the switching elements 16a, 16b, 16c, and 16d. Even if comprised in this way, the same effect can be acquired.

Embodiment 6 FIG.
FIG. 9 is a block diagram showing a configuration of a voltage bias circuit 22B according to Embodiment 6 of the present invention. In the sixth embodiment, an example in which the voltage bias circuit 22B is connected in the configurations shown in FIGS. 1, 5, and 7 will be described. As shown in FIG. 9, the voltage bias circuit 22B is connected between the resistor 22d connected between the positive bus P and the other end R of the reactor 18a, and the QS between the negative bus Q and the other end S of the reactor 18b. And the resistor 22c connected between the other end R of the reactor 18a and the other end S of the reactor 18b.

  By configuring the voltage bias circuit 22B as in the illustrated example, a voltage similar to that when the voltage bias circuit 22A is connected is generated between the RSs. The voltage bias circuit 22B provides the same effect as when the voltage bias circuit 22A is connected, and the voltage source 22a of the voltage bias circuit 22A is not necessary, so that the cost can be reduced.

Embodiment 7 FIG.
In the seventh embodiment of the present invention, switching elements 16a, 16b, 16c and 16d of the inverter circuit 2b are switched by a wide gap semiconductor such as GaN nitrogen gallium or SiC silicon carbide in the configuration shown in FIG. 1, FIG. 5 and FIG. An example of an element is shown. In general, a wide gap semiconductor has a smaller leakage current than a silicon semiconductor. Therefore, since the current flowing through the resistor 22b constituting the voltage bias circuit 22A can be reduced, the resistance value of the resistor 22b can be increased. Thereby, the effect that the power loss by resistance can be reduced is acquired. When a wide gap semiconductor is used, the withstand voltage and heat resistance are increased, and the allowable current density is also increased. Therefore, the switching elements 16a, 16b, 16c, and 16d can be downsized, and the grid-connected inverter device can be further downsized.

  As described above, the grid interconnection inverter device according to the first to seventh embodiments includes an inverter unit, a linkage switch, a control unit, a first voltage detection unit, and a second voltage detection unit. A voltage bias circuit, and the control unit opens the interconnection switch before operating the inverter unit, and detects the voltage detected by the first voltage detection unit and the second voltage detection unit. It is determined using the detected voltage whether an abnormality has occurred in the interconnection switch. With this configuration, it is possible to reliably detect a short-circuit fault in the interconnection switch before starting the operation of the inverter unit. Therefore, in order to ensure safety, there is no need to add an AC switch in addition to the interconnection switch between the inverter unit and the commercial power system, and a configuration in which one interconnection switch 3 is installed is also safe. Can be secured, and at the same time, miniaturization and cost reduction can be achieved.

  Further, the grid interconnection inverter device according to Embodiment 2 includes a third voltage detection unit that detects a voltage between one end of the interconnection switch on the commercial power system side and one DC input of the inverter unit. When the control unit determines that there is no abnormality in the interconnection switch, the control unit causes the inverter unit to output a voltage having a specific value and detects the commercial power system of the interconnection switch detected by the third voltage detection unit. When the voltage at one end on the side is equal to a voltage of a specific value, it is determined that an abnormality has occurred in the interconnection switch. With this configuration, it is possible to determine whether or not an abnormality has occurred in the contact piece on one side of the interconnecting switch, and even with the configuration in which one interconnecting switch 3 is installed, further safety is ensured. Can do.

  In addition, the control unit of the grid-connected inverter device according to the fourth embodiment outputs a voltage having a specific value to one arm in the inverter unit in a state where the interconnection switch is opened before the operation of the inverter unit. One end on the commercial power system side of the interconnection switch corresponding to one arm in the inverter unit detected by the third voltage detection unit by controlling the switching element constituting the other arm in the inverter unit to the OFF state Is equal to a voltage of a specific value output from the one arm, it is determined that an abnormality has occurred in the interconnection switch. By changing the operation of the inverter circuit in this way, it is possible to determine whether or not an abnormality has occurred in the contact piece on one side of the interconnection switch, and a configuration in which one interconnection switch 3 is installed is also possible. Therefore, further safety can be ensured.

  The configuration described in the above embodiment shows an example of the contents of the present invention, and can be combined with another known technique, and can be combined with other configurations without departing from the gist of the present invention. It is also possible to omit or change the part.

DESCRIPTION OF SYMBOLS 1a, 1b, 1c System interconnection inverter device, 2 inverter part, 2a converter circuit, 2b inverter circuit, 2c filter circuit, 3 interconnection switch, 3a, 3b, 4a, 4b contact piece, 4 independent switch, 5 independent Output terminal, 6a, 6b, 6c control unit, 7 first voltage detection unit, 9 third voltage detection unit, 11, 15, 19 capacitor, 12, 18a, 18b reactor, 13, 16a, 16b, 16c, 16d Switching element, 14 output diode, 17a, 17b arm, 20 second voltage detector, 20a, 20b voltage detector, 21 fourth voltage detector, 22A, 22B voltage bias circuit, 22a voltage source, 22b, 22c, 22d, 22e resistance, 25 solar cell, 26 commercial power system, 27 single-phase three-wire system, 27a, 27b single-phase system.

Claims (14)

An inverter unit for converting DC power into AC power;
An interconnection switch installed between the inverter unit and the commercial power system;
A control unit for controlling the inverter unit and the interconnection switch;
A first voltage detection unit for detecting a voltage at both ends of the interconnection switch on the inverter unit side;
A second voltage detector for detecting a voltage across the commercial power system side of the interconnection switch;
A voltage bias circuit for applying a bias voltage connected to both ends on the inverter side of the interconnection switch;
With
The control unit is configured such that the voltage detected by the first voltage detection unit and the voltage detected by the second voltage detection unit in a state where the interconnection switch is opened before the inverter unit is operated. And determining whether or not an abnormality has occurred in the interconnecting switch.   When the voltage detected by the second voltage detector and the bias voltage, which is the voltage detected by the first voltage detector, are equal, the controller causes an abnormality in the interconnection switch. The grid-connected inverter device according to claim 1, wherein the grid-connected inverter device is determined.   When the voltage detected by the first voltage detector and the system voltage of the commercial power system, which is the voltage detected by the second voltage detector, are equal, the controller is connected to the interconnection switch. The grid-connected inverter device according to claim 1, wherein it is determined that an abnormality has occurred.   When the voltage detected by the first voltage detector and the voltage detected by the second voltage detector are each zero volts, the control unit has an abnormality in the interconnection switch The grid interconnection inverter device according to claim 1, wherein A third voltage detection unit for detecting a voltage between one end of the interconnection switch on the commercial power system side and one DC input of the inverter unit;
When the control unit determines that no abnormality has occurred in the interconnection switch, the control unit causes the inverter unit to output a voltage having a specific value, and the interconnection switch detected by the third voltage detection unit. 2. The grid interconnection according to claim 1, wherein when the voltage at one end on the commercial power system side is equal to the voltage of the specific value, it is determined that an abnormality has occurred in the interconnection switch. Inverter device.   The control unit outputs a voltage of a specific value to one arm in the inverter unit in a state in which the interconnection switch is opened before the operation of the inverter unit, and outputs the other arm in the inverter unit. The switching element to be configured is controlled to be in an off state, and the voltage at one end on the commercial power system side of the interconnection switch corresponding to the one arm in the inverter unit detected by the third voltage detection unit is 6. The grid interconnection inverter device according to claim 5, wherein when the voltage is equal to a voltage having a specific value output from one arm, it is determined that an abnormality has occurred in the interconnection switch. A converter circuit that is installed between an external DC power supply and the inverter unit and boosts the input voltage of the inverter unit,
The control unit boosts an input voltage of the inverter unit by controlling on / off of a switching element of the converter circuit before determining whether or not an abnormality has occurred in the interconnection switch. The grid connection inverter apparatus as described in any one of Claims 1-6.   The grid-connected inverter device according to any one of claims 1 to 7, wherein the voltage bias circuit supplies a DC voltage.   2. The voltage bias circuit according to claim 1, wherein the voltage bias circuit is a circuit having an impedance that causes a current flowing to the commercial power system to be 1 milliampere or less when the interconnection switch is closed. The grid connection inverter apparatus as described in any one of claim | item 8.   10. The voltage of a specific value output from the inverter unit is a half value of a direct-current voltage input to the inverter unit. 10. Grid-connected inverter device.   2. The control unit according to claim 1, wherein when it is determined that an abnormality has occurred in the interconnection switch, the control unit displays on the display unit that the abnormality has occurred in the interconnection switch. The grid connection inverter apparatus as described in any one of 10.   The system according to any one of claims 1 to 11, wherein when the controller determines that an abnormality has occurred in the interconnection switch, the control unit stops the transition to the operation start. Interconnected inverter device.   The grid interconnection inverter device according to any one of claims 1 to 12, wherein a switching element constituting an arm of the inverter unit is formed of a wide gap semiconductor.   The grid-connected inverter device according to claim 13, wherein the wide gap semiconductor is silicon carbide.

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