Power converter

Abstract

To provide a power conversion device that can discharge a capacitor without requiring a discharge circuit. [Solution] The power conversion device A1 includes an input / output terminal section T1 and an input / output terminal section T2, an inverter circuit 1 having switching elements SW1 to SW6 and connected between the input / output terminal section T1 and the input / output terminal section T2 to convert DC power input / output to the input / output terminal section T1 and AC power input / output to the input / output terminal section T2, a control circuit 6 that controls the inverter circuit 1, a switch 31 that opens and closes the connection between the input / output terminal section T1 and the inverter circuit 1, and a switch 32 that opens and closes the connection between the input / output terminal section T2 and the inverter circuit 1. When the control circuit 6 stops the DC power to AC power conversion process, it first stops the switching of the switching elements, opens switches 31 and 32, and restarts the switching of the switching elements.

Description

Technical Field

[0001] The present invention relates to a power conversion device.

Background Art

[0002] A power conversion device that performs power conversion is known. For example, a power conversion device that converts DC power and AC power includes a capacitor on the DC side for smoothing the DC voltage. When the power conversion device stops the power conversion operation, it is necessary to discharge the charge stored in the capacitor in order to prevent an accident due to the voltage charged in the capacitor. As a method of discharging the capacitor, a method of connecting a discharge resistor in parallel with the capacitor has been devised. Also, a method has been devised in which a circuit in which a discharge resistor and a switch are connected in series is connected in parallel with the capacitor, and the discharge resistor is connected in parallel with the capacitor only when the switch is turned on.

[0003] Patent Document 1 discloses a power conversion device in which a circuit composed of a resistor and a switch element connected in series and a resistor are each connected in parallel with a smoothing capacitor. When the voltage between the terminals of the capacitor is greater than or equal to a threshold value, the power conversion device turns off the switch element and discharges using a passive discharge circuit using one resistor. On the other hand, when the voltage between the terminals is less than the threshold value, the power conversion device turns on the switch element and discharges using an active discharge circuit using two resistors.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] When a discharge resistor is connected in parallel to a capacitor as a discharge circuit, power is consumed by the discharge resistor even while the power converter is operating, resulting in wasted power loss. When a circuit consisting of a discharge resistor and a switch connected in series is connected in parallel to a capacitor as a discharge circuit, power consumption by the discharge resistor can be prevented when the switch is off. However, to account for a short-circuit failure of the switch, it is necessary to increase the size of the discharge resistor or install a fuse to prevent burnout. In this case, the power converter will also become larger due to the increased size of the discharge circuit. Furthermore, the manufacturing cost of the power converter increases due to the discharge circuit.

[0006] The present invention was conceived under the circumstances described above, and aims to provide a power conversion device that can discharge a capacitor without requiring a discharge circuit. [Means for solving the problem]

[0007] A power conversion device provided by a first aspect of the present invention comprises a first input / output terminal section and a second input / output terminal section; a power conversion circuit having a switching element and connected between the first input / output terminal section and the second input / output terminal section for converting the first input / output power of the first input / output terminal section and the second input / output power of the second input / output terminal section; a control circuit for controlling the power conversion circuit; a first switch for opening and closing the connection between the first input / output terminal section and the power conversion circuit; and a second switch for opening and closing the connection between the second input / output terminal section and the power conversion circuit, wherein when the control circuit stops the conversion process between the first input / output power and the second input / output power, it first stops the switching of the switching element, opens the first switch and the second switch, and restarts the switching of the switching element.

[0008] In a preferred embodiment of the present invention, the control circuit further comprises a capacitor that is charged during the conversion process and a voltage sensor that detects the charging voltage of the capacitor, wherein the control circuit stops the switching of the switching element when the charging voltage falls below a predetermined voltage after restarting the switching of the switching element.

[0009] In a preferred embodiment of the present invention, the power conversion circuit converts DC power input and output to the first input / output terminal and AC power input and output to the second input / output terminal, and the capacitor is connected in parallel between the power conversion circuit and the first switch.

[0010] In a preferred embodiment of the present invention, the power conversion circuit converts the DC voltage applied to the first input / output terminal and the DC voltage applied to the second input / output terminal, and the capacitor is connected in parallel between the power conversion circuit and the first switch.

[0011] In a preferred embodiment of the present invention, the power conversion circuit converts AC power input and output to the first input / output terminal and AC power input and output to the second input / output terminal, and the capacitor is included in the power conversion circuit. [Effects of the Invention]

[0012] According to the present invention, when the control circuit stops the conversion process, it first stops the switching of the switching element, opens the first and second switches, and then restarts the switching of the switching element. With the first and second switches open, the switching element performs switching, causing current to flow within the power converter. At this time, the capacitor is discharged, and power is consumed due to no-load losses, etc. Therefore, the power converter according to the present invention can discharge the capacitor without providing a discharge circuit. [Brief explanation of the drawing]

[0013] [Figure 1] This is a block diagram showing the overall configuration of the power conversion device according to the first embodiment. [Figure 2] This flowchart shows an example of a shutdown process. [Figure 3] This is a block diagram showing the overall configuration of the power conversion device according to the second embodiment. [Figure 4] This is a block diagram showing the overall configuration of the power conversion device according to the third embodiment. [Modes for carrying out the invention]

[0014] Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0015] Figure 1 is a block diagram showing the overall configuration of a power converter A1 according to the first embodiment. The power converter A1 includes a DC-side input / output terminal section T1, an AC-side input / output terminal section T2, an inverter circuit 1, a filter circuit 2, a DC-side switch 31, an AC-side switch 32, a DC capacitor 4, a control circuit 6, and a voltage sensor 71. The control circuit 6 includes a stop processing section 61 and an inverter control section 62. The power converter A1 is a so-called power conditioner. The DC-side input / output terminal section T1 of the power converter A1 is connected to a storage battery B1, and the AC-side input / output terminal section T2 is connected to a power system B2. The power converter A1 converts AC power supplied from the power system B2 or a power generation facility (not shown) into DC power to charge the storage battery B1, discharges the storage battery B1 when necessary, converts the DC power input from the storage battery B1 into AC power, and supplies it to the power system B2 or a load (not shown). The storage battery B1 is a rechargeable battery that can be repeatedly charged and discharged, for example, a lithium-ion battery. Note that battery B1 may be other rechargeable batteries such as nickel-metal hydride batteries, nickel-cadmium batteries, or lead-acid batteries. Alternatively, battery B1 may be a capacitor, such as an electric double-layer capacitor, instead of a rechargeable battery.

[0016] The inverter circuit 1 is a bidirectional power conversion circuit that converts between DC power and AC power. The DC input / output terminals of the inverter circuit 1 are connected to the battery B1 via the input / output terminal section T1, and the AC input / output terminals are connected to the filter circuit 2. The inverter circuit 1 charges and discharges the connected battery B1 in response to commands from the control circuit 6. The inverter circuit 1 charges the connected battery B1 by converting the AC power input from the AC side to DC power and outputting it to the DC side. The inverter circuit 1 also discharges the connected battery B1 by converting the DC power stored in the connected battery B1 to AC power and outputting it to the AC side.

[0017] In the illustrated example, inverter circuit 1 is a three-phase full-bridge circuit including six switching elements SW1 to SW6. In the illustrated example, each switching element SW1 to SW6 is an IGBT (Insulated-Gate Bipolar Transistor), but it is not limited to this, and other transistors such as MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors) and bipolar transistors may also be used. In inverter circuit 1, each switching element SW1 to SW6 is individually connected in antiparallel to each diode D1 to D6. Each switching element SW1 to SW6 in inverter circuit 1 receives a drive signal (e.g., a PWM signal) from the inverter control unit 62 of the control circuit 6, and is switched on and off according to the drive signal. Note that the configuration of inverter circuit 1 is not limited to a full-bridge circuit, but may also be a half-bridge circuit, for example, as long as it is a circuit capable of converting DC and AC. Furthermore, in this embodiment, since the power converter A1 is connected to a three-phase power system B2, a three-phase inverter is used as the inverter circuit 1. However, if the power converter A1 is connected to a single-phase power system or the like, a single-phase inverter is used as the inverter circuit 1.

[0018] The filter circuit 2 is connected between the inverter circuit 1 and the input / output terminal section T2. The filter circuit 2 is a low-pass filter that suppresses the output of harmonic currents due to the switching of the inverter circuit 1. The filter circuit 2 removes harmonic currents and supplies the fundamental wave current to the power system B2.

[0019] In the illustrated example, the filter circuit 2 is an LC filter including reactors L1, L2, L3 and capacitors C1, C2, C3. One terminal of the reactor L1 is connected to the connection point between the switching elements SW1 and SW2, and the other terminal is connected to one terminal of the input / output terminal section T2 via the switch 32. One terminal of the reactor L2 is connected to the connection point between the switching elements SW3 and SW4, and the other terminal is connected to the other one terminal of the input / output terminal section T2 via the switch 32. One terminal of the reactor L3 is connected to the connection point between the switching elements SW5 and SW6, and the other terminal is connected to the remaining one terminal of the input / output terminal section T2 via the switch 32. One terminal of the capacitor C1 is connected to the other terminal of the reactor L1, one terminal of the capacitor C2 is connected to the other terminal of the reactor L2, and one terminal of the capacitor C3 is connected to the other terminal of the reactor L3. The other terminals of the capacitors C1, C2, C3 are connected to each other. Note that the configuration of the filter circuit 2 is not limited to the illustrated example.

[0020] The switch 31 is connected between the input / output terminal section T1 and the inverter circuit 1. When the switch 31 is closed (on), it closes the current path between the input / output terminal section T1 and the inverter circuit 1, and when it is open (off), it cuts off the current path between the input / output terminal section T1 and the inverter circuit 1.

[0021] The switch 32 is connected between the input / output terminal section T2 and the inverter circuit 1. When the switch 32 is closed (on), it closes the current path between the input / output terminal section T2 and the inverter circuit 1, and when it is open (off), it cuts off the current path between the input / output terminal section T2 and the inverter circuit 1.

[0022] The DC capacitor 4 is connected between the switch 31 and the inverter circuit 1. One terminal of the DC capacitor 4 is connected to one input / output terminal on the DC side of the inverter circuit 1, and the other terminal is connected to the other input / output terminal on the DC side of the inverter circuit 1. That is, the DC capacitor 4 is connected in parallel between the input / output terminals on the DC side of the inverter circuit 1. Also, the DC capacitor 4 is connected in parallel between the terminals of the input / output terminal section T1 via the switch 31. The DC capacitor 4 is provided to smooth the DC voltage input / output to the inverter circuit 1 and is charged and discharged when the inverter circuit 1 performs power conversion processing. The type and capacitance of the DC capacitor 4 are not limited and are appropriately designed according to the specifications of the power conversion device A1.

[0023] The voltage sensor 71 detects the charging voltage, which is the voltage between the terminals of the DC capacitor 4. The detection value detected by the voltage sensor 71 is input to the control circuit 6 (at least the stop processing section 61).

[0024] The control circuit 6 is realized by, for example, a microcomputer or the like and controls the inverter circuit 1 and the switches 31, 32. The control circuit 6 includes a stop processing section 61 and an inverter control section 62. The stop processing section 61 and the inverter control section 62 may be implemented on a common microcomputer or may be implemented on different microcomputers respectively.

[0025] The inverter control unit 62 controls the inverter circuit 1. The inverter control unit 62 generates drive signals (e.g., PWM signals) to control the driving (switching operation) of each switching element SW1 to SW6 of the inverter circuit 1 and outputs them to each switching element SW1 to SW6. The inverter circuit 1 performs power conversion processing by having each switching element SW1 to SW6 switch according to the drive signals, thereby charging and discharging the connected storage battery B1. The specific control method of the inverter control unit 62 is not limited. Examples of control methods for the inverter control unit 62 include constant current control, constant voltage control, and constant power control.

[0026] The stop processing unit 61 performs a stop process when stopping the power conversion process of the power converter A1. The stop process includes a process to discharge the voltage charged in the DC capacitor 4. The stop process first stops the switching of each switching element SW1 to SW6 in the inverter circuit 1, then opens switches 31 and 32, and then restarts the switching of each switching element SW1 to SW6. In other words, the stop processing unit 61 first instructs the inverter control unit 62 to stop switching. The inverter control unit 62 stops the switching of each switching element SW1 to SW6 by stopping the generation or output of drive signals. As a result, each switching element SW1 to SW6 is fixed in the off state. Next, the stop processing unit 61 outputs an open command to switches 31 and 32. As a result, switches 31 and 32 are opened, and the power converter A1 is disconnected from the battery B1 and the power system B2. Even in this state, the output lines of each phase are connected to each other inside the filter circuit 2 via capacitors C1, C2, and C3. Subsequently, the stop processing unit 61 instructs the inverter control unit 62 to resume switching. The inverter control unit 62 resumes the generation and output of drive signals, thereby restarting the switching of each switching element SW1 to SW6. The control method at this time is not limited. As a result, current flows within the closed circuit of the power converter A1, consisting of the DC capacitor 4, the inverter circuit 1, and the filter circuit 2. At this time, the DC capacitor 4 is discharged, and power is consumed due to no-load losses within the closed circuit and switching losses in each switching element SW1 to SW6. At this time, the capacitors C1, C2, and C3 of the filter circuit 2 are also discharged.

[0027] As power is consumed and the DC capacitor 4 discharges, the charging voltage of the DC capacitor 4 decreases. The stop process stops the switching of each switching element SW1 to SW6 when the charging voltage falls below a predetermined voltage. The stop processing unit 61 compares the detected value of the charging voltage input from the voltage sensor 71 with the predetermined voltage. The predetermined voltage is a voltage value used to determine that the charging voltage has reached a level that is not dangerous to the human body (a so-called safe voltage), and is set in advance. The predetermined voltage is not limited, but for example, a voltage value of about 30 to 60V is set. When the detected value of the charging voltage falls below the predetermined voltage, the stop processing unit 61 instructs the inverter control unit 62 to stop switching. The inverter control unit 62 stops the switching of each switching element SW1 to SW6 by stopping the generation and output of the drive signal.

[0028] Figure 2 is a flowchart showing an example of the stop process performed by the stop processing unit 61. The stop process is initiated when the operator instructs the power conversion process to stop, or in the event of an emergency stop due to the detection of an overcurrent, etc.

[0029] First, the switching of each switching element SW1 to SW6 is stopped (S1). Specifically, the stop processing unit 61 instructs the inverter control unit 62 to stop the switching. Next, switches 31 and 32 are opened (S2). Specifically, the stop processing unit 61 outputs an open command to switches 31 and 32. Next, the switching of each switching element SW1 to SW6 is restarted (S3). Specifically, the stop processing unit 61 instructs the inverter control unit 62 to restart the switching. As a result, current flows inside the power converter A1, the DC capacitor 4 is discharged, and power is consumed due to no-load losses and switching losses.

[0030] Next, the charging voltage Vc is detected (S4). Specifically, the stop processing unit 61 acquires the detected value of the charging voltage Vc detected by the voltage sensor 71. Next, it is determined whether the charging voltage Vc is less than a predetermined voltage V0 (S5). If the charging voltage Vc is greater than or equal to the predetermined voltage V0 (S5: NO), the process returns to step S4 and steps S4 and S5 are repeated. During this time, each switching element SW1 to SW6 is switched, and the DC capacitor 4 is discharged, so the charging voltage Vc decreases. If the charging voltage Vc falls below the predetermined voltage V0 (S5: YES), the switching of each switching element SW1 to SW6 is stopped (S6), and the stop process is completed. Specifically, the stop processing unit 61 instructs the inverter control unit 62 to stop switching. Note that the process shown in the flowchart of Figure 2 is just one example, and the stop process performed by the stop processing unit 61 is not limited to those described above.

[0031] Next, the operation and effects of the power converter A1 according to this embodiment will be described.

[0032] According to this embodiment, when the stop processing unit 61 of the control circuit 6 stops the power conversion process of the inverter circuit 1, it first stops the switching of each switching element SW1 to SW6 of the inverter circuit 1, opens switches 31 and 32, and restarts the switching of each switching element SW1 to SW6. As a result, the power converter A1 is disconnected from the storage battery B1 and the power system B2, and current flows within its internal closed circuit. At this time, the DC capacitor 4 is discharged, and power is consumed due to no-load losses, etc. Therefore, the power converter A1 can discharge the DC capacitor 4 solely through control by the control circuit 6, without having a discharge circuit. Since the power converter A1 does not have a discharge circuit and therefore does not incur losses due to a discharge circuit, it is possible to achieve higher efficiency compared to conventional power converters that have a discharge circuit. Furthermore, since the power converter A1 does not have a discharge circuit, it is possible to miniaturize it and reduce manufacturing costs compared to conventional power converters that have a discharge circuit.

[0033] Furthermore, according to this embodiment, the stop processing unit 61 restarts the switching of each switching element SW1 to SW6, and then stops the switching of each switching element SW1 to SW6 when the charging voltage falls below a predetermined voltage. Therefore, the power converter A1 can discharge the DC capacitor 4 until the charging voltage reaches a safe voltage. As a result, the power converter A1 can prevent accidents caused by the voltage charged in the DC capacitor 4.

[0034] Conventional power converters also include an inverter circuit 1, a filter circuit 2, switches 31 and 32, and a voltage sensor 71. Furthermore, conventional power converters also include a control circuit for controlling the inverter circuit 1 and switches 31 and 32. In other words, power converter A1 can be configured by adding a stop processing program to the control circuit without adding any circuits to the conventional power converter. In addition, if switches 31 and 32 short-circuit, power converter A1 can detect this using the protection function already provided in the conventional power converter, so there is no need to provide a separate protection circuit for stop processing.

[0035] In this embodiment, the case in which the power converter A1 performs both DC power to AC power and AC power to DC power has been described, but it is not limited to this. The power converter A1 may perform only DC power to AC power, or only AC power to DC power. For example, if a DC power source such as a solar cell is connected instead of the battery B1, the power converter A1 only needs to perform DC power to AC power. Also, if a DC load is connected instead of the battery B1, the power converter A1 only needs to perform AC power to DC power.

[0036] Furthermore, although this embodiment describes the case where the AC side of power converter A1 is connected to power system B2, it is not limited to this. The AC side of power converter A1 may be connected to an AC load such as an AC motor. In this case, power converter A1 only needs to perform the conversion from DC power to AC power.

[0037] Figure 3 is a block diagram showing the overall configuration of the power converter A2 according to the second embodiment. In Figure 3, elements that are the same as or similar to those in the power converter A1 according to the first embodiment are denoted by the same reference numerals, and redundant explanations are omitted. The power converter A2 according to this embodiment differs from the power converter A1 according to the first embodiment in that it converts DC power to DC power of a different voltage.

[0038] In the second embodiment, the power converter A2 has an input / output terminal T2 connected to a DC load B3. Furthermore, the power converter A2 includes a DC / DC converter circuit 11 instead of an inverter circuit 1. In this embodiment, the DC / DC converter circuit 11 is a step-up / step-down converter. The specific circuit configuration of the DC / DC converter circuit 11 is not limited to that shown in the figure. The DC / DC converter circuit 11 switches a switching element SW1 in response to a drive signal input from the converter control unit 63 of the control circuit 6, thereby boosting or stepping down the voltage input from the battery B1 via the input / output terminal T1, and outputting it to the DC load B3 via the input / output terminal T2.

[0039] In this embodiment as well, when the stop processing unit 61 of the control circuit 6 stops the power conversion process of the DC / DC converter circuit 11, it first stops the switching of the switching element SW1 of the DC / DC converter circuit 11, opens switches 31 and 32, and restarts the switching of the switching element SW1. As a result, the power converter A2 is disconnected from the storage battery B1 and the DC load B3, and current flows within the internal closed circuit. At this time, the DC capacitor 4 is discharged, and power is consumed due to no-load losses, etc. Therefore, the power converter A2 can discharge the DC capacitor 4 solely through control by the control circuit 6, without having a discharge circuit. Furthermore, after restarting the switching of the switching element SW1, the stop processing unit 61 stops the switching of the switching element SW1 when the charging voltage falls below a predetermined voltage. Therefore, the power converter A2 can discharge the DC capacitor 4 until the charging voltage reaches a safe voltage. Moreover, the power converter A2 can achieve the same effects as the power converter A1 with the same configuration as the power converter A1.

[0040] In this embodiment, the case where the DC / DC converter circuit 11 is a step-up / step-down converter has been described, but it is not limited to this. The DC / DC converter circuit 11 may be a step-up converter or a step-down converter, or any other type of DC / DC converter. Also, in the description of the power conversion device A2, the case where a storage battery B1 is connected to the input / output terminal T1 has been described, but it is not limited to this. A DC power source such as a solar cell may be connected to the input / output terminal T1 instead of the storage battery B1.

[0041] Figure 4 is a block diagram showing the overall configuration of the power converter A3 according to the third embodiment. In Figure 4, elements that are the same as or similar to those in the power converter A1 according to the first embodiment are denoted by the same reference numerals, and redundant explanations are omitted. The power converter A3 according to this embodiment differs from the power converter A1 according to the first embodiment in that it converts AC power into a different type of AC power.

[0042] In the third embodiment, the power converter A3 has an input / output terminal T1 connected to an AC power source B4 and an input / output terminal T2 connected to an AC load B5. The power converter A3 also further includes a rectifier circuit 5. The rectifier circuit 5 is, for example, a full-wave rectifier circuit using diodes. The specific circuit configuration of the rectifier circuit 5 is not limited. The rectifier circuit 5 may also be any other type of rectifier circuit. The rectifier circuit 5 is connected between the switch 31 and the DC capacitor 4. The rectifier circuit 5 rectifies the AC current input from the AC power source B4 via the input / output terminal T1 and outputs the DC current to the DC capacitor 4. The rectifier circuit 5, DC capacitor 4, and inverter circuit 1 together constitute a power converter circuit (AC / AC converter circuit 12) that converts AC power to a different type of AC power.

[0043] In this embodiment as well, when the stop processing unit 61 of the control circuit 6 stops the power conversion process of the AC / AC converter circuit 12 (inverter circuit 1), it first stops the switching of each switching element SW1 to SW6 of the inverter circuit 1, opens switches 31 and 32, and restarts the switching of each switching element SW1 to SW6. As a result, the power converter A1 is disconnected from the AC power source B4 and the AC load B5, and current flows within the internal closed circuit. At this time, the DC capacitor 4 is discharged, and power is consumed due to no-load losses, etc. Therefore, the power converter A3 can discharge the DC capacitor 4 solely by control by the control circuit 6, without having a discharge circuit. Furthermore, after restarting the switching of each switching element SW1 to SW6, the stop processing unit 61 stops the switching of each switching element SW1 to SW6 when the charging voltage falls below a predetermined voltage. Therefore, the power converter A3 can discharge the DC capacitor 4 until the charging voltage reaches a safe voltage. Furthermore, power converter A3 can achieve the same effects as power converter A1 by having the same configuration as power converter A1.

[0044] In this embodiment, the case in which the AC / AC converter circuit 12 includes a rectifier circuit 5 has been described, but it is not limited to this. The AC / AC converter circuit 12 may also include an AC / DC converter circuit instead of a rectifier circuit 5. The specific circuit configuration of the AC / DC converter circuit is not limited. When the AC / DC converter circuit converts AC power to DC power by switching switching elements, the stop processing unit 61 may instruct the control unit that controls the AC / DC converter circuit to stop and restart switching, similar to the inverter control unit 62.

[0045] Furthermore, although this embodiment describes a case where the power converter A3 includes an AC / AC converter circuit 12 comprising a rectifier circuit 5, a DC capacitor 4, and an inverter circuit 1, it is not limited to this. The power converter A3 may also include, for example, a matrix converter circuit as the AC / AC converter circuit 12.

[0046] The power conversion device according to the present invention is not limited to the embodiments described above. The specific configuration of each part of the power conversion device according to the present invention can be modified in various ways. [Explanation of Symbols]

[0047] A1-A3: Power converter, 1: Inverter circuit, 11: DC / DC converter circuit, 12: AC / AC converter circuit, SW1-SW6: Switching elements, 31,32: Switches, 4: Capacitor, 6: Control circuit, 71: Voltage sensor, T1,T2: Input / output terminals

Claims

1. A first input / output terminal section and a second input / output terminal section, A power conversion circuit having a switching element and connected between the first input / output terminal section and the second input / output terminal section, which converts the first input / output power of the first input / output terminal section and the second input / output power of the second input / output terminal section, A control circuit for controlling the power conversion circuit, A first switch that opens and closes the connection between the first input / output terminal and the power conversion circuit, A second switch that opens and closes the connection between the second input / output terminal and the power conversion circuit, Equipped with, When the control circuit stops the conversion process between the first input / output power and the second input / output power, it first stops the switching of the switching element, opens the first switch and the second switch, and then restarts the switching of the switching element. Power converter.

2. A capacitor that is charged during the aforementioned conversion process, A voltage sensor for detecting the charging voltage of the capacitor, Furthermore, The control circuit, after restarting the switching of the switching element, stops the switching of the switching element when the charging voltage falls below a predetermined voltage. The power conversion device according to claim 1.

3. The power conversion circuit converts the DC power input and output to the first input / output terminal and the AC power input and output to the second input / output terminal, The capacitor is connected in parallel between the power conversion circuit and the first switch. The power conversion device according to claim 2.

4. The power conversion circuit converts the DC voltage applied to the first input / output terminal and the DC voltage applied to the second input / output terminal. The capacitor is connected in parallel between the power conversion circuit and the first switch. The power conversion device according to claim 2.

5. The power conversion circuit converts the AC power input and output to the first input / output terminal and the AC power input and output to the second input / output terminal, The capacitor is included in the power conversion circuit. The power conversion device according to claim 2.

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