Power System

Abstract

To avoid a situation in which an unintended voltage is applied to an electrical apparatus when a bidirectional power conversion device is started, according to a power supply system connected to the electrical apparatus.SOLUTION: A power supply system 110 comprises a power storage device 105, an SMR 130, a bidirectional power conversion device 170, a capacitor 146, and an ECU 190, The bi-directional power conversion device 170 connected to a power line pair PL2 through a power line pair PL3 is bi-directionally constituted between a second power line pair PL2 and electric power equipment 200 outside a vehicle 100 in a power-convertible manner. The ECU 190 is constituted so as to execute first pre-charge processing for charging the capacitor 146 before turning on the SMR 130. The bi-directional power conversion device 170 is constituted by including a switching element connected to the power line pair PL3. The ECU 190 starts the first pre-charge processing when starting the bidirectional power conversion device 170.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a power supply system, and more particularly to a power supply system connected to an electrical device. [Background technology]

[0002] Japanese Patent Laid-Open Publication No. 2009-131077 (Patent Document 1) discloses a vehicle. This vehicle includes a power storage device, a system main relay (SMR), an inverter, a motor, and a charging device. The SMR is provided between the power storage device and the inverter. The inverter drives the motor. The charging device is connected to a pair of power lines between the SMR and the inverter, and charges the power storage device using power from a power source external to the vehicle. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2009-131077 A Summary of the Invention [Problem to be solved by the invention]

[0004] The charging device as described above may be configured with a bidirectional power conversion device capable of supplying power to a power facility outside the vehicle. Unlike a power conversion device (e.g., a rectifier circuit) that has a function of charging only, the bidirectional power conversion device includes a switching element connected to a pair of power lines through which charging or supplying power flows, and a drive circuit for the switching element. When the bidirectional power conversion device is started up, a power source for the drive circuit supplies operating power to the drive circuit so that the switching element is kept in an off state. However, a voltage may be applied from this power source to the pair of power lines.

[0005] When the bidirectional power conversion device is started up before the SMR is turned on, if an unintended voltage is applied to the power line pair to which an electric device such as an inverter is connected, various problems may occur.

[0006] The present disclosure has been made to solve the above problem, and has a purpose to prevent a situation in which an unintended voltage is applied to an electric device when a bidirectional power conversion device is started up in a power supply system connected to the electric device. [Means for solving the problem]

[0007] A power supply system according to the present disclosure is connected to an electric device. The power supply system includes a power storage device, a first relay, a bidirectional power conversion device, a first capacitor, and a control device. The first relay is provided between a first power line pair connected to the power storage device and a second power line pair connected to the electric device. The bidirectional power conversion device is connected to the second power line pair through a third power line pair and configured to be capable of bidirectional power conversion between the second power line pair and an electric power facility outside the vehicle. The first capacitor is provided between the second power line pair. The control device is configured to execute a first precharge process for charging the first capacitor before turning on the first relay. The bidirectional power conversion device includes a switching element connected to the third power line pair. The control device starts the first precharge process when the bidirectional power conversion device is started.

[0008] At the time of starting up the bidirectional power converter, a voltage may be applied to the second power line pair from the power supply of the drive circuit of the switching element of the bidirectional power converter. As a result, an unintended voltage may be applied to the electrical device. With the above configuration, at the time of starting up the bidirectional power converter, precharging of the first capacitor and application of a voltage from the bidirectional power converter to the second power line pair are simultaneously executed. The voltage applied from the bidirectional power converter to the second power line pair is sufficiently smaller than the voltage of the power for precharging the first capacitor. Therefore, when the first precharge process is started as described above, the voltage from the bidirectional power converter to the second power line pair is substantially hidden by the voltage of the power for precharging the first capacitor. This makes it possible to mitigate the influence of the voltage application from the bidirectional power converter to the second power line pair on the electrical device. As a result, it is possible to avoid a situation in which an unintended voltage is applied to the electrical device at the time of starting up the bidirectional power converter before the SMR is turned on.

[0009] The bidirectional power converter may include a switching element, a drive circuit, and a bootstrap circuit. The drive circuit drives the switching element. The bootstrap circuit supplies operating power to the drive circuit.

[0010] With the above configuration, the configuration of the bidirectional power conversion device can be simplified.

[0011] The power supply system may further include a charging device, a second relay, and a second capacitor. The charging device is connected to the first power line pair and configured to convert power supplied from a power facility to charge the power storage device. The second relay is provided between the first power line pair and a fourth power line pair connected to the charging device. The second capacitor is provided between the fourth power line pair. The control device may further be configured to execute a second pre-charge process for charging the second capacitor before turning on the second relay. The control device may start the first pre-charge process prior to the second pre-charge process when both the bidirectional power conversion device and the charging device are started.

[0012] If the second precharge process is started before the first precharge process when both the bidirectional power conversion device and the charging device are started, a voltage may be applied from the bidirectional power conversion device to the second power line pair before the first capacitor is precharged. As a result, an unintended voltage may be applied to the electrical device. By using the above configuration, such a situation can be avoided. Effect of the Invention

[0013] According to the present disclosure, in a power supply system connected to an electric device, it is possible to prevent a situation in which an unintended voltage is applied to the electric device when a bidirectional power conversion device is started up. [Brief description of the drawings]

[0014] [Figure 1] 1 is a diagram showing a configuration of a vehicle equipped with a power supply system according to an embodiment. [Diagram 2] FIG. 2 is a diagram illustrating a detailed configuration of a bidirectional power conversion device. [Diagram 3] FIG. 2 is a diagram showing a detailed configuration of an AC-DC conversion circuit. [Figure 4] 5 is a timing chart for explaining an example of a process executed at the time of starting up the bidirectional power conversion device and the charging device. [Diagram 5] 5 is a timing chart for explaining a process executed by an ECU when starting up a bidirectional power conversion device and a charging device. [Figure 6] 4 is a flowchart showing an example of a process executed by an ECU in relation to external charging. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are designated by the same reference characters and their description will not be repeated.

[0016] [Embodiment Mode] Fig. 1 is a diagram showing the configuration of a vehicle equipped with a power supply system according to this embodiment. With reference to Fig. 1, a vehicle 100 includes a DC (Direct Current) / DC converter 121, an auxiliary battery 122, electrical equipment 107, and a power supply system 110.

[0017] The DC / DC converter 121 is connected to a power line pair PL2 that connects the SMR 130 and an inverter 125 (both of which will be described later). The DC / DC converter 121 converts the power flowing through the power line pair PL2 into power at a voltage level (12 V) for the auxiliary battery 122. The DC / DC converter 121 can also convert power provided from the auxiliary battery 122 into power at a voltage level for the electric devices 107, and supply the converted power to the power line pair PL2.

[0018] The electric equipment 107 includes a compressor 124, an inverter 125, and a motor 127. The compressor 124 is connected to the power line pair PL2 and is used for air conditioning in the vehicle 100. The inverter 125 is connected to the power line pair PL2 and drives the motor 127. The motor 127 is connected to the inverter 125 and generates driving force for running the vehicle 100.

[0019] Power supply system 110 is connected to electric equipment 107, and includes a power storage device 105, a voltage sensor 106, an SMR 130, capacitors 146 and 148, voltage sensors 147 and 149, and a bidirectional power converter 170. Power supply system 110 further includes an inlet 192, a socket 195, a charging device 180, a charging relay 185, and an ECU (Electronic Control Unit) 190.

[0020] The power storage device 105 is a secondary battery such as a lithium ion battery, and stores electric power for running the vehicle 100. The voltage sensor 106 detects the voltage VB of the power storage device 105.

[0021] The SMR130 is provided between the power line pair PL1 connected to the power storage device 105 and the power line pair PL2 connected to the electrical equipment 107. The SMR130 switches between electrical connection and disconnection between the power line pair PL1, PL2. The SMR130 includes relays RL1 to RL3 and a limiting resistor R1. The "off state" of the SMR130 is a state in which the relays RL1 to RL3 are open. The "on state" of the SMR130 is a state in which the relays RL1 and RL2 are closed. "Turning on" the SMR130 means switching the SMR130 from the off state to the on state.

[0022] The capacitor 146 is provided between the pair of power lines PL2 and is used to smooth the voltage VL1 between the pair of power lines PL2. The voltage sensor 147 detects the voltage VL1.

[0023] Bidirectional power converter 170 is connected to power line pair PL2 via power line pair PL3, to inlet 192 (described below) via power line pair PL3A, and to outlet 195 (described below) via power line pair PL3B.

[0024] The bidirectional power converter 170 is configured to perform bidirectional power conversion between the power line pair PL2 and a power equipment 200 outside the vehicle 100. The bidirectional power converter 170 functions as a charging device that converts power received from the power equipment 200 through the inlet 192, supplies the power to the power line pair PL3, and charges the power storage device 105 through the power line pair PL2 and the SMR 130 (external charging of the vehicle 100). On the other hand, the bidirectional power converter 170 also functions as a power feeding device that converts power received from the power storage device 105 through the power line pairs PL1, PL2, PL3, and supplies the power to the power equipment 200 through the inlet 192 or to the electric load 250 through the outlet 195 (external power feeding of the vehicle 100).

[0025] The inlet 192 is configured to connect to the power equipment 200 through the connector 205 and the power line pair PL0. When the connector 205 is inserted into the inlet 192, external charging or external power supply from the vehicle 100 to the power equipment 200 becomes possible.

[0026] The outlet 195 is configured to be connected to an electric load 250 outside the vehicle 100 via a plug 255 of the electric load 250. When the plug 255 is inserted into the outlet 195, external power supply from the vehicle 100 to the electric load 250 becomes possible.

[0027] The charging device 180 is used to increase the charging power of the power storage device 105. Specifically, when the charging device 180 operates during external charging in addition to the bidirectional power conversion device 170, the charging power can be increased (the charging time can be shortened) compared to when only the bidirectional power conversion device 170 operates.

[0028] Whether or not the charging device 180 operates may be determined according to the rated output power of the power equipment 200. For example, the operating state of the charging device 180 may be determined such that when the output power is large, the charging device 180 operates in addition to the bidirectional power conversion device 170, whereas when the output power is small, the charging device 180 does not operate (only the bidirectional power conversion device 170 operates).

[0029] Charging device 180 is connected to power line pair PL3A through power line pair PL3C, and is provided electrically in parallel with bidirectional power conversion device 170. Charging device 180 is connected to power line pair PL1 through power line pair PL4, a charging relay 185 (described later), and power line pair PL1A. Charging device 180 is configured to charge power storage device 105 by converting power supplied from power equipment 200 through inlet 192 and power line pair PL3C.

[0030] Charging relay 185 is connected to power line pair PL1 through power line pair PL1A, and is provided electrically in parallel with SMR 130. Charging relay 185 is provided between power line pair PL1 and power line pair PL4 connected to charging device 180. Charging relay 185 includes relays RL11 to RL13 and limiting resistor R2. The "off state" of charging relay 185 is a state in which relays RL11 to RL13 are open. The "on state" of charging relay 185 is a state in which relays RL11 and RL12 are closed. "Turning on" charging relay 185 means switching charging relay 185 from the off state to the on state.

[0031] The capacitor 148 is provided between the power line pair PL4 and is used to smooth the voltage VL2 between the power line pair PL4. The voltage sensor 149 detects the voltage VL2.

[0032] The power line pairs PL1, PL2, and PL3, the SMR 130, the bidirectional power conversion device 170, and the charging device 180 configure a high-voltage system of the vehicle 100.

[0033] The ECU 190 includes a CPU (Central Processing Unit) and a memory (neither shown). The CPU executes various types of arithmetic processing. The memory includes a ROM (Read Only Memory) and a ROM (Random Access Memory). The ROM stores programs executed by the CPU. The RAM functions as a working memory.

[0034] The ECU 190 controls each device of the vehicle 100, such as the electric devices 107, the SMR 130, the bidirectional power conversion device 170, the charging device 180, and the charging relay 185. For example, when the connector 205 is inserted into the inlet 192, the ECU 190 starts up the high voltage system (permits the start of this system) before external charging. Then, the ECU 190 performs external charging by turning on the SMR 130 and the charging relay 185 and activating both the bidirectional power conversion device 170 and the charging device 180.

[0035] ECU 190 executes a switching process for SMR 130 and charging relay 185 according to the detected values ​​of the voltages of the power line pairs (for example, voltages VB, VL1, VL2).

[0036] The ECU 190 executes, for example, a first precharge process for charging the capacitor 146 before turning on the SMR 130. In this example, the first precharge process is a process for precharging the capacitor 146 by causing the DC / DC converter 121 to supply precharge power to the power line pair PL2.

[0037] ECU 190 executes a second pre-charge process for charging capacitor 148 before turning on charging relay 185. The second pre-charge process is a process for controlling relay RL13 to a closed state before controlling relay RL12 to a closed state after controlling relay RL11 to a closed state. As a result, capacitor 148 is pre-charged by power storage device 105 in a situation where the current is limited by limiting resistor R2.

[0038] Fig. 2 is a diagram showing a detailed configuration of the bidirectional power conversion device 170. Referring to Fig. 2, the bidirectional power conversion device 170 includes relays 1702 and 1703, an AC (Alternating Current)-DC conversion circuit 1705, an inverter 1710, a transformer 1715, and an AC-DC conversion circuit 1720.

[0039] The relay 1702 is controlled to a closed state during external charging or during external power supply from the vehicle 100 to the power equipment 200. The relay 1703 is controlled to a closed state during external power supply from the vehicle 100 to the electric load 250. The AC-DC conversion circuit 1705 converts the AC power received by the inlet 192 into DC power. The inverter 1710 converts the DC power from the AC-DC conversion circuit 1705 into AC power. The transformer 1715 performs power transmission between the inverter 1710 and the AC-DC conversion circuit 1720 while electrically insulating them from each other.

[0040] AC-DC conversion circuit 1720 converts AC power from transformer 1715 into DC power and supplies the converted power to power line pair PL2 through power line pair PL3. AC-DC conversion circuit 1720 can also convert DC power supplied from power storage device 105 through power line pair PL1, SMR 130, and power line pair PL3 into AC power and supply the converted power to power equipment 200 or electrical load 250 through transformer 1715.

[0041] Fig. 3 is a diagram showing a detailed configuration of the AC-DC conversion circuit 1720. With reference to Fig. 3, the AC-DC conversion circuit 1720 includes switching elements Q1-Q4, diodes D1-D4, drive circuits CR1-CR4, a power supply PS, and bootstrap circuits 1725 and 1730.

[0042] Each of the switching elements Q1 to Q4 is a MOSFET (Metal Oxide Semiconductor Field Effect Transistor) in this example, and is connected to the power line pair PL3. Diodes D1 to D4 are connected in anti-parallel to the switching elements Q1 to Q4, respectively.

[0043] The drive circuits CR1 to CR4 are configured to drive the gates of the switching elements Q1 to Q4, respectively. The drive circuits CR1 to CR4 each output an off hold signal to the switching elements Q1 to Q4 so that the voltage from the transformer 1715 is not supplied to the power line pair PL2 through the power line pair PL3 before the start of external charging. The off hold signals are output to the gates of the switching elements Q1 to Q4, respectively, to keep the switching elements Q1 to Q4 in the off state. The power source PS is provided to supply operating power to the drive circuits CR3 and CR4.

[0044] The bootstrap circuits 1725 and 1730 include a diode D11 and a capacitor C11, and a diode D12 and a capacitor C12, respectively. The bootstrap circuits 1725 and 1730 are configured to supply operating power to the drive circuits CR1 and CR2 using a power supply PS, respectively. Specifically, power from the power supply PS is supplied to the capacitors C11 and C12 through the diodes D11 and D12, respectively. The power stored in the capacitors C11 and C12 is then used as operating power for the drive circuits CR1 and CR2, respectively.

[0045] In this way, when the bidirectional power converter 170 includes the bootstrap circuits 1725 and 1730, a single power source PS can supply operating power to the drive circuits CR1 to CR4. This makes it possible to simplify the configuration of the bidirectional power converter 170 compared to the case where a plurality of power sources supply operating power to the drive circuits CR1 to CR4.

[0046] 4 is a timing chart for explaining an example of the processing executed at the start-up of the bidirectional power conversion device 170 and the charging device 180. In this example, the second pre-charge processing (pre-charge of the capacitor 148) is executed prior to the first pre-charge processing (pre-charge of the capacitor 146). This example is a comparative example in which the control by the ECU 190 described later is not executed.

[0047] With reference to Fig. 4, the horizontal axis represents time. Time t0 is the time when connector 205 is inserted into inlet 192, and at this time, both SMR 130 and charging relay 185 are off. The vertical axis represents, from the top, start / stop of bidirectional power conversion device 170, start / stop of charging device 180, voltage VL2, on / off of charging relay 185, voltage VL1, and on / off of SMR 130. In the following description, Figs. 1 to 3 will be referred to as appropriate.

[0048] At time t1, the ECU of the comparative example activates the high-voltage system (including the bidirectional power converter 170 and the charging device 180) of the vehicle 100. As a result, the power supply PS of the bidirectional power converter 170 is activated. Then, the voltage from the power supply PS is applied to the power line pair PL2 via the power line pair PL3 through the bootstrap circuit 1725, the diode D1, the bootstrap circuit 1730, and the diode D2. As a result, the voltage VL1 changes from 0 to VA (0 < VA << VB). In this example, VA is shown as being constant for ease of illustration, but in reality, VA can vary within a range greater than 0 and sufficiently smaller than VB. Thus, applying a voltage (VA) to the power line pair PL2 before the first pre-charge process is not intended.

[0049] At time t1, the ECU starts the second pre-charge process by switching the relays RL11 and RL13 from the open state to the closed state. Then, until time t2 arrives (until the voltage VL2 reaches the voltage VB), the ECU executes the second pre-charge process. And at time t3, the ECU turns on the charging relay 185 by opening the relay RL13 and closing the relay RL12.

[0050] At time t4, the ECU starts the first pre-charge process by starting the operation of the DC / DC converter 121. Then, until time t5 arrives (until the voltage VL1 reaches the voltage VB), the ECU executes the first pre-charge process. And at time t6, the ECU turns on the SMR130. Then, external charging starts.

[0051] In the above comparative example, the second pre-charge process is executed prior to the first pre-charge process when the bidirectional power converter 170 is activated before external charging (at time t1). As a result, a voltage is applied to the power line pair PL2 from the bootstrap circuits 1725 and 1730 of the bidirectional power converter 170 before the execution of the first pre-charge process (before time t4). As a result, an unintended voltage (VA) is applied to the power line pair PL2.

[0052] The power supply system 110 according to the present embodiment has a configuration for dealing with the above problem. Specifically, the ECU 190 starts the first precharge process when the bidirectional power converter 170 is started. With this configuration, when the bidirectional power converter 170 is started, the precharge of the capacitor 146 and the application of a voltage from the bidirectional power converter 170 to the power line pair PL2 are simultaneously executed. The voltage applied from the bidirectional power converter 170 to the power line pair PL2 is sufficiently smaller than the voltage of the precharge power from the DC / DC converter 121 to the capacitor 146. Therefore, when the first precharge process is started as described above, the voltage from the bidirectional power converter 170 to the power line pair PL2 is substantially hidden by the voltage of the precharge power of the capacitor 146. This makes it possible to mitigate the influence on the electric devices 107 caused by the application of the voltage from the bidirectional power converter 170 to the power line pair PL2.

[0053] In this embodiment, the ECU 190 starts both the bidirectional power conversion device 170 and the charging device 180 before external charging. Then, when both the bidirectional power conversion device 170 and the charging device 180 are started, the ECU 190 starts the first precharge process prior to the second precharge process. If the second precharge process is started prior to the first precharge process, as in the comparative example, a voltage may be applied from the bootstrap circuits 1725 and 1730 to the power line pair PL2 prior to the first precharge process, and an unintended voltage may be applied to an electric device such as the inverter 125. In contrast, in the embodiment, the first precharge process is executed prior to the second precharge process and at the time of starting up the bidirectional power conversion device 170. As a result, it is possible to avoid an unintended voltage application to an electric device.

[0054] Fig. 5 is a timing chart for explaining the process executed by the ECU 190 when the bidirectional power conversion device 170 and the charging device 180 are started up. With reference to Fig. 5, the horizontal axis and the vertical axis are the same as those in the comparative example (Fig. 4). Times t10 and t11 are the same as times t0 and t1 in the comparative example, respectively.

[0055] At time t11, the ECU 190 starts both the bidirectional power converter 170 and the charging device 180 and starts a first precharge process. As a result, when the bidirectional power converter 170 is started, precharging of the capacitor 146 and application of a voltage from the bidirectional power converter 170 to the power line pair PL2 are simultaneously performed. As a result, the voltage from the bidirectional power converter 170 to the power line pair PL2 is substantially hidden by the voltage of the power for precharging the capacitor 146. Therefore, it is possible to avoid the generation of an unintended voltage in the power line pair PL2.

[0056] The ECU 190 executes the first pre-charge process until time t12 arrives (until the voltage VL1 reaches the voltage VB). At time t13, the ECU 190 turns on the SMR .

[0057] At time t14, ECU 190 starts the second pre-charge process. Thereafter, ECU 190 executes the second pre-charge process until time t15 arrives (until voltage VL2 reaches voltage VB). Then, at time t16, ECU 190 turns on charging relay 185. Thereafter, external charging starts.

[0058] Fig. 6 is a flowchart showing an example of processing related to external charging and executed by ECU 190. The processing of this flowchart starts when connector 205 is inserted into inlet 192. In the following description, Fig. 5 will be referred to as appropriate.

[0059] 6, at time t11, the ECU 190 starts up the bidirectional power conversion device 170 and the charging device 180 (step S105) and starts a first pre-charge process (step S110).

[0060] Next, ECU 190 determines whether precharging of capacitor 146 has been completed (step S115). Specifically, ECU 190 executes this determination process according to whether voltage VL1 has reached voltage VB. If precharging has not yet been completed (NO in step S115), ECU 190 executes the above determination process until precharging is completed. On the other hand, if precharging has been completed (YES in step S115), ECU 190 turns on SMR 130 at time t13 (step S120).

[0061] Next, the ECU 190 starts the second pre-charge process at time t14 (step S125).

[0062] Next, ECU 190 determines whether precharging of capacitor 148 has been completed (step S130). Specifically, ECU 190 executes this determination process according to whether voltage VL2 has reached voltage VB. If precharging has not yet been completed (NO in step S130), ECU 190 executes the above determination process until precharging is completed. On the other hand, if precharging has been completed (YES in step S130), ECU 190 turns on charging relay 185 at time t16 (step S135). Then, ECU 190 starts external charging (step S140).

[0063] As described above, according to this embodiment, it is possible to prevent a situation in which an unintended voltage is applied from the power supply PS to electric devices such as the inverter 125 through the bootstrap circuits 1725, 1730 when the bidirectional power conversion device 170 is started up before the SMR 130 is turned on.

[0064] [Variations] The first pre-charge process may be a process of controlling relay RL3 to a closed state before controlling relay RL2 to a closed state after controlling relay RL1 of SMR 130 to a closed state. That is, the first pre-charge process may be executed without using DC / DC converter 121, similar to the second pre-charge process.

[0065] The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present invention is defined by the claims, not the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0066] 100 vehicle, 105 power storage device, 107 electrical equipment, 110 power supply system, 146, 148, C11, C12 capacitors, 170 bidirectional power conversion device, 180 charging device, 185 charging relay, 1725, 1730 bootstrap circuit, CR1, CR2, CR3, CR4 drive circuit, PL0, PL1A, PL1, PL2, PL3, PL3A, PL3C, PL3B, PL4 power line pair, PS power supply.

Claims

1. A power supply system connected to an electrical device, comprising: A power storage device; a first relay provided between a first pair of power lines connected to the power storage device and a second pair of power lines connected to the electric device; a bidirectional power conversion device connected to the second power line pair via a third power line pair and configured to be capable of bidirectional power conversion between the second power line pair and an electric power facility outside the vehicle; a charging device connected to the first power line pair and configured to convert power supplied from the power equipment to charge the power storage device; a second relay provided between the first power line pair and a fourth power line pair connected to the charging device; a first capacitor provided between the second pair of power lines; a second capacitor provided between the fourth power line pair; a control device configured to execute a first pre-charge process of charging the first capacitor before turning on the first relay, and a second pre-charge process of charging the second capacitor before turning on the second relay; the bidirectional power conversion device includes a switching element connected to the third power line pair, The control device starts the first pre-charge process prior to the second pre-charge process when both the bidirectional power conversion device and the charging device are started.

2. The bidirectional power converter includes: The switching element; A drive circuit that drives the switching element; 2. The power supply system of claim 1, further comprising a bootstrap circuit for supplying operating power to said drive circuit.

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