Power conversion device including inrush current prevention circuit

Abstract

To provide a power conversion device which has the same redundancy as a conventional product but is smaller and less expensive than the conventional product.SOLUTION: A power conversion device 10A includes: an inverter unit 60; a control unit 90A for controlling main switches RL1 to RL3 and inrush current prevention circuits RL4, RL5, R4, and R5; and a control power supply unit 80 for driving the control unit 90A by using power supplied from DC power buses Ndc1, Ndc2. When detecting that the output of a DC power supply unit 30 is insufficient during steady operation, the control unit 90A switches auxiliary switches RL4, RL5 to a closed state after switching the main switches RL1, RL3 to an open state, so that the power from a commercial power system is supplied to the DC power buses Ndc1, Ndc2 through the auxiliary switches RL4, RL5, the resistors R4, R5, and diodes D1 to D3 in the inverter unit 60.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a power conversion device connected to a commercial power system and provided with an inrush current prevention circuit.

Background Art

[0002] Fig. 4 shows a conventional power conversion device 100. The power conversion device 100 includes an AC breaker 101 having one end connected to a commercial power system 200 and a household load 201, a system connection relay 102 having one end connected to the other end of the AC breaker 101, a bidirectional AC / DC inverter 104 having AC side input / output terminals connected to the other end of the system connection relay 102, a bus line precharge circuit 103 (inrush current prevention circuit) connected in parallel with the system connection relay 102, a bus line 105 connected to the DC side input / output terminals of the inverter circuit 104, a capacitor 106 connected to the bus line 105, and a bidirectional DC / DC converter 107 having one input / output terminal connected to the bus line 105. A battery module 202 is connected to the other input / output terminal of the bidirectional DC / DC converter 107.

[0003] The power conversion device 100 further includes a control unit 108 that controls the bus line precharge circuit 103, the bidirectional AC / DC inverter 104, and the bidirectional DC / DC converter 107, and a control power supply 109 that drives the control unit 108. The control power supply 109 is connected to the other end of the AC breaker 101 and can drive the control unit 108 using the AC power supplied from the commercial power system 200 via the AC breaker 101. Further, the control power supply 109 is also connected to the bus line 105 and can drive the control unit 108 using the DC power supplied from the bus line 105. According to this configuration, it is considered that the control unit 108 can continue to be driven even if one of the supply of AC power from the commercial power system 200 and the supply of DC power from the bus line 105 is interrupted.

Prior Art Documents

Patent Documents

[0004] [Patent Document 1] Japanese Patent No. 6074188 [Summary of the Invention] [Problems to be Solved by the Invention]

[0005] To make the control power supply 109 an insulated type following an example of a general control power supply, two insulation circuits (i.e., an insulation circuit for AC power input and an insulation circuit for DC power input) must be provided in the control power supply 109. This leads to an increase in the size and cost of the control power supply 109, and thus the power conversion device 100.

[0006] The present invention has been made in view of such circumstances, and an object thereof is to provide a power conversion device that has redundancy equivalent to that of conventional products but is smaller and less expensive than conventional products. [Means for Solving the Problems]

[0007] In order to solve the above problems, a power conversion device according to the present invention includes a DC power supply unit, a DC power bus connected to the DC power supply unit, an inverter unit having DC-side input / output terminals connected to the DC power bus, a capacitor connected to the DC power bus, an AC power line having one end connected to the AC-side input / output terminals of the inverter unit and the other end being connectable to a commercial power system, a main switch interposed in the AC power line, and an inrush current prevention circuit connected in parallel with the main switch. The device further includes a control unit that controls the inverter unit, the main switch, and the inrush current prevention circuit, and a control power supply unit that drives the control unit using the power supplied from the DC power bus. The inrush current prevention circuit has a sub-switch and a resistor connected in series. The inverter unit has at least one diode that enables power supply from the AC-side input / output terminals to the DC-side input / output terminals. During normal operation, the control unit keeps the main switch closed and the sub-switch open. When it detects that the output of the DC power supply unit is insufficient during normal operation, it switches the main switch to the open state and then switches the sub-switch to the closed state, so that the power of the commercial power system is supplied to the DC power bus through the sub-switch, the resistor, and the diode.

[0008] In this configuration, when the output of the DC power supply unit is insufficient, the power of the commercial power system is supplied to the control power supply unit through the sub-switch, the resistor, the diode of the inverter unit, and the DC power bus. Otherwise, the power of the DC power supply unit is supplied to the control power supply unit through the DC power bus. Therefore, according to this configuration, redundancy equivalent to that of conventional products can be obtained. Also, according to this configuration, an insulation circuit for AC power input can be omitted from the control power supply unit.

[0009] The control unit of the above power conversion device may detect, for example, that the output of the DC power supply unit is insufficient through communication with the DC power supply unit.

[0010] The above power conversion device may further include an LC filter unit interposed in the AC power line so as to be located between the main switch and the inverter unit.

[0011] When the above power conversion device includes an LC filter section, the inrush prevention circuit preferably further has a diode connected in series to the sub-switch and the resistor so as to be in the forward direction when the power of the commercial power system is supplied to the DC power bus.

[0012] According to this configuration, it is possible to suppress the reactive power due to the capacitor included in the LC filter section.

Effect of the Invention

[0013] According to the present invention, it is possible to provide a power conversion device that is smaller and less expensive than conventional products while having redundancy equivalent to that of conventional products.

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

Figure 3

Figure 4

Mode for Carrying Out the Invention

[0015] Hereinafter, a first embodiment and a second embodiment of a power conversion device according to the present invention will be described with reference to the accompanying drawings.

[0016] [First Embodiment] Fig. 1 shows a power conversion device 10A according to the first embodiment of the present invention. As shown in the same figure, the power conversion device 10A according to this embodiment includes a terminal block 20A connected to a single-phase three-wire commercial power system during use, a DC power supply unit 30, and a connection switching unit 40A, an LC filter unit 50A, an inverter unit 60, and a voltage adjustment unit 70 that are connected in series between them. The power conversion device 10A can output the power output by the DC power supply unit 30 toward the commercial power system via the terminal block 20A. Further, when the DC power supply unit 30 includes a secondary battery, the power conversion device 10A can also charge the secondary battery of the DC power supply unit 30 with the power of the commercial power system input via the terminal block 20A.

[0017] The DC power supply unit 30 can output DC power to the DC power buses Ndc1 and Ndc2. In this embodiment, the DC power supply unit 30 is composed of a solar cell that outputs DC power according to the solar radiation amount and a DC / DC converter that converts the DC power output by the solar cell into a predetermined DC power and outputs it to the DC power buses Ndc1 and Ndc2. In this embodiment, when there is sufficient solar radiation and the DC / DC converter is operating normally (that is, when the DC power supply unit 30 can output a predetermined DC power), the voltage of the DC power buses Ndc1 and Ndc2 becomes 350 [V].

[0018] The connection switching unit 40A includes a main switch RL1 interposed in the U-phase AC power line Nac1 connected to the terminal block 20A, a main switch RL2 interposed in the W-phase AC power line Nac2 connected to the terminal block 20A, and a main switch RL3 interposed in the O-phase AC power line Nac3 connected to the terminal block 20A. The main switches RL1 to RL3 are composed of a-contact relays. Therefore, when the control by the control unit 90A described later is not performed, the main switches RL1 to RL3 are in an open state.

[0019] The connection switching unit 40A further includes an inrush current prevention circuit (RL4, R4) connected in parallel with the main switch RL1 and an inrush current prevention circuit (RL5, R5) connected in parallel with the main switch RL2. RL4 and RL5 are auxiliary switches composed of b-contact relays. Therefore, when not controlled by the control unit 90A described later, the auxiliary switches RL4 and RL5 are in the closed state. R4 connected in series with the auxiliary switch RL4 and R5 connected in series with the auxiliary switch RL5 are resistors for current limitation.

[0020] The LC filter unit 50A includes an inductor L1 interposed in the AC power line Nac1, an inductor L2 interposed in the AC power line Nac2, a capacitor C1 connected to the AC power lines Nac1 and Nac2, a capacitor C2 connected to the AC power lines Nac1 and Nac3, and a capacitor C3 connected to the AC power lines Nac2 and Nac3.

[0021] The inverter unit 60 includes six switching elements SW1 to SW6, three diodes D1 to D3, DC side input / output terminals T1 and T2 connected to the DC power buses Ndc1 and Ndc2, and AC side input / output terminals T3 and T4 connected to the AC power lines Nac1 and Nac2.

[0022] The switching elements SW1 to SW6 are composed of N-channel IGBTs (Insulated Gate Bipolar Transistors). The collector of the switching element SW1 is connected to the DC-side input / output terminal T1, and the emitter is connected to the AC-side input / output terminal T4. The collector of the switching element SW2 is connected to the emitter of the switching element SW1, and the emitter is connected to the DC-side input / output terminal T2. The collector of the switching element SW3 is connected to the DC-side input / output terminal T1, and the emitter is connected to the AC-side input / output terminal T3. The collector of the switching element SW4 is connected to the emitter of the switching element SW3, and the emitter is connected to the DC-side input / output terminal T2. Also, the emitter of the switching element SW5 is connected to the AC-side input / output terminal T4, and the collector is connected to the DC-side input / output terminal T1 via the diode D3. The emitter of the switching element SW6 is connected to the AC-side input / output terminal T3, and the collector is connected to the DC-side input / output terminal T1 via the diode D3.

[0023] The anode of the diode D1 is connected to the emitter of the switching element SW5, and the cathode is connected to the collector of the switching element SW5. The anode of the diode D2 is connected to the emitter of the switching element SW6, and the cathode is connected to the collector of the switching element SW6. Also, the anode of the diode D3 is connected to the collectors of the switching elements SW5 and SW6, and the cathode is connected to the DC-side input / output terminal T1. The diodes D1 and D2 may be the body diodes of the switching elements SW5 and SW6.

[0024] When the voltage at the AC-side input / output terminal T3 is approximately 1.5 [V] higher than the voltage at the DC-side input / output terminal T1, current flows from the AC-side input / output terminal T3 to the DC-side input / output terminal T1 through the diodes D2 and D3. Also, when the voltage at the AC-side input / output terminal T4 is approximately 1.5 [V] higher than the voltage at the DC-side input / output terminal T1, current flows from the AC-side input / output terminal T4 to the DC-side input / output terminal T1 through the diodes D1 and D3. Therefore, it can be said that the diodes D1 to D3 are diodes that enable power supply from the AC-side input / output terminals T3 and T4 to the DC-side input / output terminals T1 and T2.

[0025] When the control by the control unit 90A described later is not being performed, the switching elements SW1 to SW6 are in the off state.

[0026] The voltage adjustment unit 70 includes two switching elements SW7 and SW8, two capacitors C4 and C5, and an inductor L3.

[0027] The switching elements SW7 and SW8 are composed of N-channel IGBTs, similar to the switching elements SW1 to SW6. The collector of the switching element SW7 is connected to the DC power bus Ndc1. The collector of the switching element SW8 is connected to the emitter of the switching element SW7 and the emitter is connected to the DC power bus Ndc2. One end of the capacitor C4 is connected to the DC power bus Ndc1 and the other end is connected to the AC power line Nac3. One end of the capacitor C5 is connected to the other end of the capacitor C4 and the other end is connected to the DC power bus Ndc2. Also, one end of the inductor L3 is connected to the AC power line Nac3 and the other end is connected to the emitter of the switching element SW7 (and the collector of the switching element SW8).

[0028] When the control by the control unit 90A described later is not being performed, the switching elements SW7 and SW8 are in the off state.

[0029] The power conversion device 10A according to this embodiment further includes a control power supply unit 80 and a control unit 90A.

[0030] The control unit 90A is composed of an MPU (Micro Processing Unit) or the like, and controls the connection switching unit 40A, the inverter unit 60, and the voltage adjustment unit 70. Specifically, the control unit 90A can open and close the main switches RL1 to RL3 and the sub-switches RL4 and RL5 of the connection switching unit 40A, turn on / off the switching elements SW1 to SW6 of the inverter unit 60, and turn on / off the switching elements SW7 and SW8 of the voltage adjustment unit 70.

[0031] When the control unit 90A opens and closes the main switches RL1 to RL3 and the sub-switches RL4 and RL5, the inverter unit 60 and the like are disconnected from the commercial power system, connected to the commercial power system via the main switches RL1 to RL3, or connected to the commercial power system via the sub-switches RL4 and RL5.

[0032] When the control unit 90A turns on / off the switching elements SW1 to SW6, the inverter unit 60 performs a DC→AC conversion operation of converting the DC power supplied from the DC side input / output terminals T1 and T2 into AC power and outputting it from the AC side input / output terminals T3 and T4, and an AC→DC conversion operation of converting the AC power supplied from the AC side input / output terminals T3 and T4 into DC power and outputting it from the DC side input / output terminals T1 and T2. When performing this control, the control unit 90A refers to the measured values of voltage meters and ammeters (not shown) provided in each part of the power conversion device 10A.

[0033] When the control unit 90A turns on / off the switching elements SW7 and SW8, the voltage generated across the capacitor C4 and the voltage generated across the capacitor C5 become equal. Conversely, the control unit 90A turns on / off the switching elements SW7 and SW8 so that the voltage generated across the capacitor C4 and the voltage generated across the capacitor C5 become equal. When performing this control, the control unit 90A refers to the measured values of voltage meters and ammeters (not shown) provided in each part of the power conversion device 10A.

[0034] The control unit 90A can also communicate with the DC power supply unit 30 periodically and acquire information regarding the operating state of the DC power supply unit 30. In the present embodiment, the control unit 90A acquires the voltage value between the solar cell and the DC / DC converter, which indicates the power generation status of the solar cell.

[0035] The control power supply unit 80 is composed of a power supply circuit including an insulation circuit for DC power input from the DC power buses Ndc1 and Ndc2, that is, a power supply circuit including one insulation circuit. The control power supply unit 80 drives the control unit 90A using the power supplied from the DC power buses Ndc1 and Ndc2. The control power supply unit 80 can drive the control unit 90A only when the voltage of the DC power buses Ndc1 and Ndc2 (= the potential of the DC power bus Ndc1 - the potential of the DC power bus Ndc2) exceeds a preset minimum voltage (hereinafter referred to as "operation lower limit voltage").

[0036] Subsequently, an operation example of the power conversion device 10A according to the present embodiment will be described. In this operation example, the initial state is a state in which the solar cell of the DC power supply unit 30 is not substantially generating power due to low solar radiation and the terminal block 20A is not connected to the commercial power system. In this initial state, since the voltages of the DC power buses Ndc1 and Ndc2 are 0 [V] (that is, voltages lower than the aforementioned operation lower limit voltage), the control power supply unit 80 is not driving the control unit 90A. Also, since the control unit 90A is not performing control, the main switches RL1 to RL3 of the connection switching unit 40A are in the open state, the sub - switches RL4 and RL5 of the connection switching unit 40A are in the closed state, the switching elements SW1 to SW6 of the inverter unit 60 are in the off state, and the switching elements SW7 and SW8 of the voltage adjustment unit 70 are in the off state.

[0037] When the terminal block 20A is connected to the commercial power system in the initial state, the capacitors C4 and C5 connected to the DC power buses Ndc1 and Ndc2 are charged through the paths of the sub - switch RL4 → resistor R4 → inductor L1 → diode D2 → diode D3 and the sub - switch RL5 → resistor R5 → inductor L2 → diode D1 → diode D3, and the voltages of the DC power buses Ndc1 and Ndc2 increase.

[0038] The current flowing from the commercial power system towards capacitors C4 and C5 is restricted by resistors R4 and R5. Therefore, when the terminal block 20A is connected to the commercial power system, excessive current does not flow through the sub-switching devices RL4, RL5, etc. Conversely, the resistance values of resistors R4 and R5 are set such that the current flowing through the sub-switching devices RL4, RL5, etc. is less than the maximum allowable current value.

[0039] When the voltages of the DC power buses Ndc1 and Ndc2 exceed the operating lower limit voltage, the control power supply unit 80 starts driving the control unit 90A. That is, the supply of power from the control power supply unit 80 to the control unit 90A begins.

[0040] The control unit 90A, which receives power supply from the control power supply unit 80, acquires the voltage value between the solar cell and the DC / DC converter through communication with the DC power supply unit 30.

[0041] When the acquired voltage value exceeds the level at which the voltages of the DC power buses Ndc1 and Ndc2 can be maintained at 350 [V], that is, when it is detected that the output of the DC power supply unit 30 is sufficient, the main switching devices RL1 to RL3 are switched from the open state to the closed state, and immediately thereafter, the sub-switching devices RL4 and RL5 are switched from the closed state to the open state. Also, in this case, the control unit 90A starts controlling the switching elements SW1 to SW6 for causing the inverter unit 60 to perform the DC→AC conversion operation or the AC→DC conversion operation, and controlling the switching elements SW7 and SW8 for matching the voltages generated across the capacitors C4 and C5.

[0042] On the other hand, when the acquired voltage value is below the level at which the voltages of the DC power buses Ndc1 and Ndc2 can be maintained at 350 [V], that is, when it is detected that the output of the DC power supply unit 30 is insufficient, the above control is not performed. As a result, the charging paths of the sub-switching device RL4 → resistor R4 → inductor L1 → diode D2 → diode D3 and the sub-switching device RL5 → resistor R5 → inductor L2 → diode D1 → diode D3 are maintained.

[0043] The control unit 90A periodically communicates with the DC power supply unit 30, and continues to maintain the two charging paths until the acquired voltage value exceeds the level at which the voltages of the DC power buses Ndc1 and Ndc2 can be maintained at 350 [V]. Thereby, it is possible to prevent the supply of power to the control unit 90A from being interrupted.

[0044] During the process of the voltages of the DC power buses Ndc1 and Ndc2 rising to 350 [V], when the difference between the voltage of the AC side input / output terminal T3 and the voltage of the DC side input / output terminal T1 of the inverter unit 60, and the difference between the voltage of the AC side input / output terminal T4 and the voltage of the DC side input / output terminal T1 of the inverter unit 60 become less than about 1.5 [V], the supply of power from the commercial power system to the control power supply unit 80 stops, and the control power supply unit 80 starts to drive the control unit 90A using the power supplied from the DC power supply unit 30.

[0045] The control unit 90A also periodically communicates with the DC power supply unit 30 even during the steady operation when the voltages of the DC power buses Ndc1 and Ndc2 are 350 [V]. When the acquired voltage value is lower than the level at which the voltages of the DC power buses Ndc1 and Ndc2 can be maintained at 350 [V], that is, when it is detected that the output of the DC power supply unit 30 is insufficient, the main switches RL1 to RL3 are switched from the closed state to the open state, and immediately thereafter, the sub-switches RL4 and RL5 are switched from the open state to the closed state. Also, in this case, the control unit 90A stops the control of the switching elements SW1 to SW6 for causing the inverter unit 60 to perform the DC→AC conversion operation or the AC→DC conversion operation, and the control of the switching elements SW7 and SW8 for making the voltages generated across the capacitors C4 and C5 equal.

[0046] When the control unit 90A switches the sub - switches RL4 and RL5 from the open state to the closed state, a state is established in which power can be supplied from the commercial power system to the control power supply unit 80. Note that this power supply starts when the voltage of the DC power buses Ndc1 and Ndc2 drops, and when the voltage at the DC - side input / output terminal T1 is approximately 1.5 [V] or more lower than the voltage at the AC - side input / output terminal T3, and when the voltage at the DC - side input / output terminal T1 is approximately 1.5 [V] or more lower than the voltage at the AC - side input / output terminal T4.

[0047] Thus, in the power conversion device 10A according to the first embodiment of the present invention, either the power of the DC power supply unit 30 or the power of the commercial power system is supplied to the control power supply unit 80 without interruption from the DC power buses Ndc1 and Ndc2. Also, in the power conversion device 10A, the control power supply unit 80 does not include an insulation circuit for AC power input. Therefore, according to this embodiment, it is possible to provide a power conversion device 10A that is smaller and less expensive than conventional products while having redundancy equivalent to that of conventional products.

[0048] [Second Embodiment] FIG. 2 shows a power conversion device 10B according to the second embodiment of the present invention. As shown in the figure, the power conversion device 10B according to this embodiment includes a terminal block 20B connected to a single - phase two - wire commercial power system during use, a DC power supply unit 30, a connection switching unit 40B, an LC filter unit 50B, an inverter unit 60, a capacitor C6, a control power supply unit 80, and a control unit 90B, which are connected in series between them. That is, the power conversion device 10B differs from the power conversion device 10A in that it includes a terminal block 20B instead of the terminal block 20A, a connection switching unit 40B instead of the connection switching unit 40A, an LC filter unit 50B instead of the LC filter unit 50A, a capacitor C6 instead of the voltage adjustment unit 70, and a control unit 90B instead of the control unit 90A, but is common with the power conversion device 10A in other respects.

[0049] The connection switching unit 40B includes a main switch RL1 installed in the U-phase AC power line Nac1 connected to the terminal block 20B, and a main switch RL2 installed in the W-phase AC power line Nac2 connected to the terminal block 20B. The main switches RL1 and RL2 are composed of a-contact relays. Therefore, when the control by the control unit 90B is not performed, the main switches RL1 and RL2 are in the open state.

[0050] The connection switching unit 40B further includes an inrush current prevention circuit (RL4, R4) connected in parallel with the main switch RL1, and an inrush current prevention circuit (RL5, R5) connected in parallel with the main switch RL2. RL4 and RL5 are sub-switches composed of b-contact relays. Therefore, when the control by the control unit 90B is not performed, the sub-switches RL4 and RL5 are in the closed state. R4 connected in series with the sub-switch RL4 and R5 connected in series with the sub-switch RL5 are resistors for current limitation.

[0051] The LC filter unit 50B includes an inductor L1 installed in the AC power line Nac1, an inductor L2 installed in the AC power line Nac2, and a capacitor C1 connected to the AC power lines Nac1 and Nac2.

[0052] The inverter unit 60 includes six switching elements SW1 to SW6, three diodes D1 to D3, DC-side input / output terminals T1 and T2 connected to the DC power buses Ndc1 and Ndc2, and AC-side input / output terminals T3 and T4 connected to the AC power lines Nac1 and Nac2. When the control by the control unit 90B is not performed, the switching elements SW1 to SW6 are in the off state.

[0053] One end of the capacitor C6 is connected to the DC power bus Ndc1 and the other end is connected to the DC power bus Ndc2.

[0054] The control unit 90B is composed of an MPU or the like, and controls the connection switching unit 40B and the inverter unit 60. Specifically, the control unit 90B can open and close the main switches RL1, RL2 and the auxiliary switches RL4, RL5 of the connection switching unit 40B, and can turn on / off the switching elements SW1 to SW6 of the inverter unit 60.

[0055] When the control unit 90B opens and closes the main switches RL1, RL2 and the auxiliary switches RL4, RL5, the inverter unit 60 and the like are disconnected from the commercial power system, connected to the commercial power system via the main switches RL1, RL2, or connected to the commercial power system via the auxiliary switches RL4, RL5.

[0056] When the control unit 90B turns on / off the switching elements SW1 to SW6, the inverter unit 60 performs a DC→AC conversion operation of converting the DC power supplied from the DC side input / output terminals T1, T2 into AC power and outputting it from the AC side input / output terminals T3, T4, and an AC→DC conversion operation of converting the AC power supplied from the AC side input / output terminals T3, T4 into DC power and outputting it from the DC side input / output terminals T1, T2. When performing this control, the control unit 90B refers to the measured values of voltmeters and ammeters (not shown) provided in each part of the power conversion device 10B.

[0057] The control unit 90B can also communicate with the DC power supply unit 30 periodically and acquire information regarding the operating state of the DC power supply unit 30. In this embodiment, the control unit 90B acquires the voltage value between the solar cell and the DC / DC converter, which indicates the power generation status of the solar cell.

[0058] Similar to the control unit 90A, the control unit 90B controls the connection switching unit 40B based on the information obtained through communication with the DC power supply unit 30.

[0059] According to the power conversion device 10B according to this embodiment, the same operational effects as those of the power conversion device 10A according to the first embodiment can be obtained.

[0060] [Modification Example] As described above, the first and second embodiments of the power conversion device according to the present invention have been explained, but the configuration of the present invention is not limited to these.

[0061] For example, the power conversion device according to the present invention may include a connection switching unit 40C shown in Fig. 3(A) instead of the connection switching unit 40A, or may include a connection switching unit 40D shown in Fig. 3(B) instead of the connection switching unit 40B. The connection switching unit 40C is different from the connection switching unit 40A in that it further includes a diode D4 provided between the auxiliary switch RL4 and the resistor R4. The diode D4 is provided in a direction that becomes forward when supplying power from the commercial power system to the DC power buses Ndc1 and Ndc2. The same applies to the connection switching unit 40D. According to these configurations, it is possible to suppress the reactive power by the capacitors C1 to C3 included in the LC filter unit 50A and the reactive power by the capacitor C1 included in the LC filter unit 50B.

[0062] Also, the power conversion device according to the present invention may include an inverter circuit different in form from the inverter unit 60. However, the inverter circuit that can be used as the inverter unit 60 must include at least one diode that enables power supply from the AC side input / output terminals T3 and T4 to the DC side input / output terminals T1 and T2.

[0063] Also, the power conversion device according to the present invention may be any other device that can output DC power to the DC power buses Ndc1 and Ndc2. Examples of such devices include various secondary batteries, combinations of various secondary batteries and bidirectional DC / DC converters, and the like.

Explanation of symbols

[0064] 10A, 10B Power conversion device 20A, 20B Terminal block 30 DC power supply unit 40A, 40B, 40C, 40D Connection switching unit 50A, 50B LC filter unit 60 Inverter unit 70 Voltage regulator 80 Control power supply unit 90A, 90B Control unit RL1, RL2, RL3 Main switch RL4, RL5 Sub-switch

Claims

1. A power conversion device comprising a DC power supply unit, a DC power bus connected to the DC power supply unit, an inverter unit having a DC-side input / output terminal connected to the DC power bus, a capacitor connected to the DC power bus, an AC power line having one end connected to the AC-side input / output terminal of the inverter unit and the other end connectable to a commercial power system, a main switch interposed in the AC power line, and an inrush current prevention circuit connected in parallel with the main switch, a control unit for controlling the inverter unit, the main switch, and the inrush current prevention circuit, a control power supply unit for driving the control unit using the power supplied from the DC power bus, further comprising, the inrush current prevention circuit having a sub-switch and a resistor connected in series, the inverter unit having at least one diode enabling supply of power from the AC-side input / output terminal to the DC-side input / output terminal, the control unit keeping the main switch in a closed state and the sub-switch in an open state during normal operation, and when detecting that the output of the DC power supply unit is insufficient during the normal operation, switching the main switch to an open state and then switching the sub-switch to a closed state so that the power of the commercial power system is supplied to the DC power bus through the sub-switch, the resistor, and the diode, characterized in that.

2. The control unit detects that the output of the DC power supply unit is insufficient through communication with the DC power supply unit. The power conversion device according to claim 1, characterized in that.

3. further comprising an LC filter unit interposed in the AC power line, the LC filter unit being located between the main switch and the inverter unit. The power conversion device according to claim 1, characterized in that.

4. The inrush prevention circuit further has a diode connected in series with the sub-switch and the resistor so as to be in the forward direction when the power of the commercial power system is supplied to the DC power bus. The power conversion device according to claim 3, characterized in that.

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