JP7711546B2 - charging device - Google Patents

Description

The present invention relates to a charging device.

Patent Document 1 discloses a power supply device that includes a first connection terminal connected to the P terminal of a DC charger between a first switching element and a second switching element of one of three phases, and a second connection terminal connected to the N terminal of the DC charger between a third switching element and a fourth switching element of the other phase, and that also functions as a charging device capable of charging a storage battery with a DC charger.

JP 2021-048759 A

If the voltages of the two smoothing capacitors connected in series to the storage battery become unbalanced while the storage battery is being charged by a DC charger, the capacitors may become overcharged, and it may be necessary to stop the charging operation before the storage battery is fully charged, so there is room for improvement.

The present invention was made in consideration of the above problems, and its purpose is to provide a charging device that can continue charging a storage battery without stopping the charging operation before charging is completed due to overcharging of the capacitor.

In order to solve the above-mentioned problems and achieve the object, the charging device according to the present invention has a capacitor section in which a first capacitor and a second capacitor are connected in series between a positive terminal and a negative terminal of a storage battery, a first switching element, a second switching element, a third switching element, and a fourth switching element connected in series, a first diode having a cathode side connected to a wiring connecting the first switching element and the second switching element and an anode side connected to a wiring connecting the first capacitor and the second capacitor, and a second diode having an anode side connected to a wiring connecting the third switching element and the fourth switching element and a cathode side connected to a wiring connecting the first capacitor and the second capacitor, and a three-level switching device capable of selectively outputting one of three different voltage values to a motor generator by turning on and off the first switching element, the second switching element, the third switching element, and the fourth switching element, respectively. A charging device including a power converter connected in parallel to the storage battery for three phases, U, V, and W, a control device for controlling the on/off switching of each switching element of the power converter, a first connection terminal electrically connected to the P terminal of a DC charger between the first switching element and the second switching element in the three-level inverter of any one of the U, V, and W phases, and a second connection terminal electrically connected to the N terminal of the DC charger between the third switching element and the fourth switching element in the three-level inverter of the other one of the U, V, and W phases. The charging device is characterized in that it includes a balancer circuit connected in parallel to the storage battery and the capacitor unit between the storage battery and the capacitor unit, and when the voltage of one of the first capacitor and the second capacitor exceeds a preset threshold, it transfers charge from one of the first capacitor and the second capacitor to the other capacitor.

In the charging device according to the present invention, while the storage battery is being charged by the DC charger, the voltage of one of the capacitors can be reduced by transferring charge from one of the capacitors that has exceeded the threshold to the other capacitor using a balancer circuit. Therefore, in the charging device according to the present invention, the voltage of one of the capacitors can be prevented from reaching the capacitor upper limit voltage, and the charging operation can be continued until the storage battery is fully charged.

In the above, the balancer circuit may be configured with a first balancer switching element, a second balancer switching element, and a reactor, the first balancer switching element and the second balancer switching element being connected in series between the positive terminal and the negative terminal of the storage battery, one side of the reactor being connected between the first balancer switching element and the second balancer switching element, and the other side of the reactor being connected between the first capacitor and the second capacitor, and the control device may be configured to control the on/off switching of the first balancer switching element and the second balancer switching element based on the voltage of the first capacitor or the second capacitor.

As a result, the control device can switch the first balancer switching element and the second balancer switching element of the balancer circuit on and off based on the voltage of the first capacitor or the second capacitor, thereby transferring charge from one capacitor to the other capacitor via the reactor.

In the above, the control device may be configured to turn on the first balancer switching element and turn off the second balancer switching element when the voltage of the first capacitor exceeds the threshold value, and then turn off the first balancer switching element and turn on the second balancer switching element at a predetermined timing.

As a result, some of the charge of the first capacitor is stored in the reactor, causing the voltage of the first capacitor to decrease, and then the charge of the first capacitor that was stored in the reactor is transferred to the second capacitor, causing the voltage of the second capacitor to increase, thereby reducing the voltage imbalance between the first capacitor and the second capacitor.

In the above, the control device may be configured to turn on the second balancer switching element and turn off the first balancer switching element when the voltage of the second capacitor exceeds the threshold value, and then turn off the second balancer switching element and turn on the first balancer switching element at a predetermined timing.

As a result, some of the charge of the second capacitor is stored in the reactor, causing the voltage of the second capacitor to decrease, and then the charge of the second capacitor that was stored in the reactor is transferred to the first capacitor, causing the voltage of the first capacitor to increase, thereby reducing the voltage imbalance between the first and second capacitors.

The charging device according to the present invention has the advantage that it can continue charging the storage battery without stopping the charging operation before the charging is completed due to overcharging of the capacitor.

FIG. 1 is a configuration diagram of a power system according to an embodiment. FIG. 2 is a block diagram showing the configuration of the power system according to the embodiment. FIG. 3 is a diagram showing the circuit state when the battery is charged by the DC charger. FIG. 4 is a diagram showing voltage waveforms when a voltage imbalance occurs during charging and the balancer circuit is not driven. FIG. 5 is a diagram showing voltage waveforms when the balancer circuit is driven in the event of a voltage imbalance occurring during charging. FIG. 6 is a diagram showing a circuit state when the first switching element is turned on and the second switching element is turned off in the balancer circuit. FIG. 7 is a diagram showing a circuit state when the first switching element is turned off and the second switching element is turned on in the balancer circuit.

The following describes an embodiment of the charging device according to the present invention. Note that the present invention is not limited to this embodiment.

Figure 1 is a configuration diagram of a power system according to an embodiment. The power system according to the embodiment is applied to electric vehicles that can run on electricity, such as electric vehicles, hybrid vehicles, PHEVs (Plug-in Hybrid Electric Vehicles), and REEVs (Range Extended Electric Vehicles).

The power system according to the embodiment is composed of a charging device 10, a motor generator 20, a DC charger 30, and the like. In the power system according to the embodiment, the charging device 10 and the motor generator 20 are mounted on the electric vehicle, and the DC charger 30 is provided in an external charging facility or the like installed outside the electric vehicle.

The charging device 10 includes a battery 12, a capacitor section 16, an inverter 18, a balancer circuit 26, a charging relay device 40, and an ECU (Electronic Control Unit) 60. The charging device 10 is electrically connected to the motor generator 20, and also functions as a power supply device that supplies power from the battery 12 to the motor generator 20.

Battery 12 is a high-voltage battery that can be charged and discharged. For example, a lithium-ion battery pack, a nickel-metal hydride battery pack, a nickel-cadmium battery, a lead-acid battery, etc. can be used as battery 12. In FIG. 1, "VB" is the battery voltage. It is desirable for the battery voltage of battery 12 to be, for example, 400 V or higher.

The capacitor section 16 is composed of a first capacitor C1 and a second capacitor C2 connected in series between the positive terminal (positive bus 22) of the battery 12 and the negative terminal (negative bus 24) of the battery 12. The first capacitor C1 and the second capacitor C2 are connected to each other at the neutral point NP1. That is, the first capacitor C1 has one terminal connected to the positive bus 22 and the other terminal connected to the neutral point NP1. The second capacitor C2 has one terminal connected to the neutral point NP1 and the other terminal connected to the negative bus 24. Therefore, if the first capacitor C1 and the second capacitor C2 are charged and discharged in the same way and always store the same charge, the neutral point voltage, which is the voltage between the neutral point NP1 and the negative bus 24, will be clamped to a voltage that is half the voltage of the battery 12. The neutral point voltage corresponds to the voltage VC2, which is the terminal voltage of the second capacitor C2. Also, VC1 in Figure 1 is the terminal voltage of the first capacitor C1.

The inverter 18 is a power converter and is composed of an upper arm to which a positive voltage, which is the voltage between the positive bus 22 and the neutral point NP1, is supplied, and a lower arm to which a negative voltage, which is the voltage between the neutral point NP1 and the negative bus 24, is supplied. In the inverter 18, the upper arm and the lower arm are multiplexed and arranged in series between the positive bus 22 and the negative bus 24, making it possible to output three-level three-phase AC voltages to the motor generator 20.

The inverter 18 also has a U-phase arm that outputs a U-phase voltage to the motor generator 20, a V-phase arm that outputs a V-phase voltage to the motor generator 20, and a W-phase arm that outputs a W-phase voltage to the motor generator 20.

In the U-phase arm, the first switching element SU1, the second switching element SU2, the third switching element SU3, and the fourth switching element SU4 are connected in series in this order from the positive bus 22 to the negative bus 24. The first switching element SU1, the second switching element SU2, the third switching element SU3, and the fourth switching element SU4 are configured with a freewheeling diode inversely parallel to the semiconductor element. Note that the reverse connection means, for example, that the cathode terminal of the diode is connected to the collector terminal of the semiconductor element, and the anode terminal of the diode is connected to the emitter terminal of the semiconductor element. The intermediate point PU1 (first intermediate point) as a connection part in the wiring connecting the first switching element SU1 and the second switching element SU2, and the intermediate point PU2 (second intermediate point) as a connection part in the wiring connecting the third switching element SU3 and the fourth switching element SU4 are connected by the diodes DU1 and DU2 such that the anode side of the two diodes DU1 and DU2 connected in series is connected to the intermediate point PU2 and the cathode side is connected to the intermediate point PU1. The connection point in the wiring connecting the two diodes DU1 and DU2 is connected to the neutral point NP1 of the capacitor unit 16. In other words, the diode DU1 has its cathode side connected to the intermediate point PU1 and its anode side connected to the neutral point NP1. The diode DU2 has its anode side connected to the intermediate point PU2 and its cathode side connected to the neutral point NP1. In this configuration, a U-phase voltage is output to the motor generator 20 from the connection point between the second switching element SU2 and the third switching element SU3.

In the V-phase arm, the first switching element SV1, the second switching element SV2, the third switching element SV3, and the fourth switching element SV4 are connected in series in this order from the positive bus 22 to the negative bus 24. The first switching element SV1, the second switching element SV2, the third switching element SV3, and the fourth switching element SV4 are configured such that a free-wheeling diode is inversely parallel to the semiconductor element. The intermediate point PV1 (first intermediate point) as a connection part in the wiring connecting the first switching element SV1 and the second switching element SV2, and the intermediate point PV2 (second intermediate point) as a connection part in the wiring connecting the third switching element SV3 and the fourth switching element SV4 are connected by the diodes DV1 and DV2 such that the anode side of the two diodes DV1 and DV2 connected in series is connected to the intermediate point PV2, and the cathode side is connected to the intermediate point PV1. The connection point of the wiring connecting these two diodes DV1 and DV2 is connected to the neutral point NP1 of the capacitor section 16. In other words, the cathode side of the diode DV1 is connected to the midpoint PV1, and the anode side is connected to the neutral point NP1. The anode side of the diode DV2 is connected to the midpoint PV2, and the cathode side is connected to the neutral point NP1. In this configuration, the V-phase voltage is output to the motor generator 20 from the connection point between the second switching element SV2 and the third switching element SV3.

In the W-phase arm, the first switching element SW1, the second switching element SW2, the third switching element SW3, and the fourth switching element SW4 are connected in series in this order from the positive bus 22 to the negative bus 24. The first switching element SW1, the second switching element SW2, the third switching element SW3, and the fourth switching element SW4 are configured with a free-wheeling diode inversely parallel to the semiconductor element. The intermediate point PW1 (first intermediate point) as a connection part in the wiring connecting the first switching element SW1 and the second switching element SW2, and the intermediate point PW2 (second intermediate point) as a connection part in the wiring connecting the third switching element SW3 and the fourth switching element SW4 are connected by the diodes DW1 and DW2 so that the anode side of the two diodes DW1 and DW2 connected in series is connected to the intermediate point PW2 and the cathode side is connected to the intermediate point PW1. The connection point of the wiring connecting these two diodes DW1 and DW2 is connected to the neutral point NP1 of the capacitor section 16. In other words, the cathode side of the diode DW1 is connected to the midpoint PW1, and the anode side is connected to the neutral point NP1. The anode side of the diode DW2 is connected to the midpoint PW2, and the cathode side is connected to the neutral point NP1. In this configuration, the W-phase voltage is output to the motor generator 20 from the connection point between the second switching element SW2 and the third switching element SW3.

In this embodiment, each switching element of the inverter 18 can be an IGBT (Insulated Gate Bipolar Transistor) or the like.

The motor generator 20 is a rotating electric machine mounted on the electric vehicle, and acts as a motor when the DC voltage output from the battery 12 is converted to a three-phase AC voltage by the inverter 18 and supplied, generating a driving force for running the vehicle. On the other hand, the motor generator 20 acts as a generator when the vehicle is braked, recovering braking energy and outputting it as a three-phase AC voltage. This three-phase AC voltage is then converted to a DC voltage by the inverter 18 and supplied to the battery 12, thereby charging the battery 12.

The DC charger 30 is an external charger provided outside the vehicle to charge the battery 12. The DC charger 30 has two terminals, a P terminal (positive terminal) 32P and an N terminal (negative terminal) 32N, which are electrically connected to the charging device 10 at a charger connection section 50 for connecting a plug (not shown) of the DC charger 30 to a connector (not shown) on the vehicle side. Between the charger connection section 50 and the inverter 18, a charging relay device 40 having a charging relay 42P and a charging relay 42N, and a reactor 44P are provided. Note that Vchg in FIG. 1 is the charger voltage.

As shown in FIG. 1, the P terminal 32P of the DC charger 30 is electrically connected to the midpoint PV1 between the first switching element SV1 and the second switching element SV2 in the V-phase arm via a charging relay 42P and a reactor 44P. The N terminal 32N of the DC charger 30 is electrically connected to the midpoint PU2 between the third switching element SU3 and the fourth switching element SU4 in the U-phase arm via a charging relay 42N.

In the charging device 10 according to the embodiment, the intermediate points PU1, PV1, and PW1, which are the first intermediate points in the three-level inverter of any one of the U-phase, V-phase, and W-phase arms, are connected to the P terminal 32P of the DC charger 30, and the intermediate points PU2, PV2, and PW2, which are the second intermediate points in the three-level inverter of the other phase, are connected to the N terminal 32N of the DC charger 30.

In this manner, in the charging device 10 according to the embodiment, a first intermediate point in the three-level inverter of any one of the U-phase arm, V-phase arm, and W-phase arm is used as a first connection terminal electrically connected to the P terminal 32P of the DC charger 30. Also, a second intermediate point in the three-level inverter of the other of the U-phase arm, V-phase arm, and W-phase arm is used as a second connection terminal electrically connected to the N terminal 32N of the DC charger 30.

The charging device 10 according to the embodiment is configured to be able to charge the battery 12 by the DC charger 30 in accordance with a plurality of voltage standards by electrically connecting the P terminal 32P of the DC charger 30 between the first switching element and the second switching element (first midpoint) in the three-level inverter of any one of the U-phase, V-phase, and W-phase of the inverter 18, and electrically connecting the N terminal 32N of the DC charger 30 between the third switching element and the fourth switching element (second midpoint) in the three-level inverter of the other phase. In addition, in the charging device 10 according to the embodiment, since the DC charger 30 is connected to the existing terminal that connects the motor generator 20 and the inverter 18, it is possible to realize the existing three-level inverter having a voltage dividing capacitor without processing the inverter 18 or adding internal wiring, and therefore it is possible to reduce costs. In addition, since a capacitor with high voltage resistance or additional parts are not required, it is possible to reduce costs and part size.

The balancer circuit 26 is connected between the battery 12 and the capacitor section 16 in parallel with them, and is composed of a first switching element SB1 which is the first balancer switching element, a second switching element SB2 which is the second balancer switching element, and a reactor 28.

The first switching element SB1 and the second switching element SB2 are connected in series between the positive terminal (positive bus 22) of the battery 12 and the negative terminal (negative bus 24) of the battery 12. The first switching element SB1 and the second switching element SB2 are connected to each other at the neutral point NP2. That is, the first switching element SB1 has one terminal connected to the positive bus 22 and the other terminal connected to the neutral point NP2. The second switching element SB2 has one terminal connected to the neutral point NP2 and the other terminal connected to the negative bus 24.

One terminal of the reactor 28 is connected to the neutral point NP2, and the other terminal is connected to the neutral point NP1 of the capacitor section 16.

The balancer circuit 26 is a circuit for eliminating the voltage imbalance between the first capacitor C1 and the second capacitor C2 of the capacitor section 16 by switching the first switching element SB1 and the second switching element SB2 on and off.

Figure 2 is a block diagram showing the configuration of the power system according to the embodiment. The ECU 60 is an electronic control device that controls the operation of the charging device 10 and other components. The ECU 60 includes a charging control unit 62 and a gate signal generating unit 64.

The charging control unit 62 receives various signals, such as a charging power command signal output from a system control unit (not shown), a voltage phase signal output from a voltmeter (not shown) provided in the inverter 18, the voltage VC1 and VC2 signals of the first capacitor C1 and the second capacitor C2 output from a voltmeter (not shown) provided in the capacitor unit 16, and a charger information signal output from the DC charger 30. The charging control unit 62 also outputs, for example, a duty calculated based on the charging power command signal, the voltage phase signal, and the voltage VC1 and VC2 signals to the gate signal generating unit 64. The gate signal generating unit 64 generates a gate signal for switching each switching element of the inverter 18 between on and off, and outputs the generated gate signal to each switching element. The gate signal generating unit 64 also generates a gate signal for switching each switching element of the balancer circuit 26 between on and off, and outputs the generated gate signal to each switching element.

Figure 3 shows the circuit state when the battery 12 is charged by the DC charger 30. In Figure 3, switching elements that are in the ON state are circled, and switching elements that are in the OFF state are not circled.

As shown in FIG. 3, when the battery 12 is charged by the DC charger 30, the ECU 60 first switches the fourth switching element SU4 of the U-phase arm and the first switching element SW1 of the W-phase arm from off to on, and keeps the other switching elements off. Next, the ECU 60 switches the charging relays 42P, 42N of the charging relay device 40 from off to on, supplying DC voltage from the DC charger 30 to the battery 12 via the inverter 18, and charging the battery 12.

The fourth switching element SU4 and the first switching element SV1 may be turned off because current flows through their respective freewheel diodes. This causes all switching elements of the inverter 18 to be turned off, eliminating the need to perform a switching operation to switch each switching element of the inverter 18 between on and off, improving charging efficiency and reducing the need to add inverter elements or cooling mechanisms for charging. On the other hand, turning on the fourth switching element SU4 and the first switching element SV1 makes it possible to ensure durability when current flows through the fourth switching element SU4 and the first switching element SV1. In addition, since the on and off states of each switching element of the inverter 18 are fixed during charging, switching losses can be reduced.

Figure 4 shows the voltage waveform when a voltage imbalance occurs during charging and the balancer circuit is not activated.

When the battery 12 is simply charged by the DC charger 30, a voltage imbalance between the first capacitor C1 and the second capacitor C2 may cause the voltage of one of the capacitors to reach the capacitor upper limit voltage due to overcharging. When the voltage of one of the capacitors reaches the capacitor upper limit voltage in this way, in order to prevent the capacitor from being damaged, it is necessary to stop charging the battery 12 even though charging is not complete.

Figure 5 shows the voltage waveform when the balancer circuit is activated if a voltage imbalance occurs during charging.

In the charging device 10 according to the embodiment, when the voltage of one of the first capacitor C1 and the second capacitor C2 exceeds a preset threshold due to a voltage imbalance between the first capacitor C1 and the second capacitor C2 while the battery 12 is being charged by the DC charger 30, the balancer circuit 26 is driven. Note that the threshold is set to a voltage lower than the preset capacitor upper limit voltage so that the first capacitor C1 and the second capacitor C2 are not damaged.

In FIG. 5, when the voltage of the first capacitor C1 exceeds the threshold due to a voltage imbalance between the first capacitor C1 and the second capacitor C2, the balancer circuit 26 is driven to transfer the charge of the first capacitor C1 to the second capacitor C2, thereby lowering the voltage of the first capacitor C1 and preventing the voltage of the first capacitor C1 from reaching the upper battery voltage limit.

Below, using Figures 6 and 7, we will explain how to move the charge of the first capacitor C1 to the second capacitor C2 by driving the balancer circuit 26.

Figure 6 is a diagram showing the circuit state when the first switching element SB1 is turned on and the second switching element SB2 is turned off in the balancer circuit 26. Figure 7 is a diagram showing the circuit state when the first switching element SB1 is turned off and the second switching element SB2 is turned on in the balancer circuit 26. Note that Figures 6 and 7 focus on the capacitor section 16 and balancer circuit 26 in the charging device 10.

First, as shown in FIG. 6, the ECU 60 turns on the first switching element SB1 and turns off the second switching element SB2 in the balancer circuit 26. As a result, a closed circuit is formed in which a current flows through the first capacitor C1, the first switching element SB1, and the reactor 28 as shown by the arrow A in FIG. 6. At this time, a part of the charge of the first capacitor C1 is stored in the reactor 28, and the voltage of the first capacitor C1 drops. After that, as shown in FIG. 7, the ECU 60 turns off the first switching element SB1 and turns on the second switching element SB2 in the balancer circuit 26 at a predetermined timing. As a result, a closed circuit is formed in which a current flows through the second capacitor C2, the reactor 28, and the second switching element SB2 as shown by the arrow B in FIG. At this time, the charge of the first capacitor C1 stored in the reactor 28 moves to the second capacitor C2, and the voltage of the second capacitor C2 increases. This reduces the voltage imbalance between the first capacitor C1 and the second capacitor C2.

In addition, in the charging device 10 according to the embodiment, the ECU 60 repeatedly switches the first switching element SB1 and the second switching element SB2 of the balancer circuit 26 on and off, thereby transferring the charge of the first capacitor C1 to the second capacitor C2, thereby eliminating the voltage imbalance between the first capacitor C1 and the second capacitor C2.

In the charging device 10 according to the embodiment, when the voltage of the first capacitor C1 exceeds the threshold value while the DC charger 30 is charging the battery 12, the balancer circuit 26 is driven to move the charge of the first capacitor C1 to the second capacitor C2, thereby preventing the voltage of the first capacitor C1 from reaching the capacitor upper limit voltage. Therefore, the charging device 10 according to the embodiment can continue charging the battery 12 without stopping the charging operation before the charging of the battery 12 is completed due to overcharging of the first capacitor C1.

In addition, in the charging device 10 according to the embodiment, when the voltage of the second capacitor C2 exceeds the threshold value while the battery 12 is being charged by the DC charger 30, the balancer circuit 26 is driven to transfer the charge of the second capacitor C2 to the first capacitor C1.

First, the ECU 60 turns on the second switching element SB2 and turns off the first switching element SB1 in the balancer circuit 26. This forms a closed circuit in which a current flows through the second capacitor C2, the reactor 28, and the second switching element SB2. At this time, a part of the charge of the second capacitor C2 is stored in the reactor 28, and the voltage of the second capacitor C2 drops. After that, the ECU 60 turns off the second switching element SB2 and turns on the first switching element SB1 in the balancer circuit 26 at a predetermined timing. This forms a closed circuit in which a current flows through the first capacitor C1, the first switching element SB1, and the reactor 28. At this time, the charge of the second capacitor C2 stored in the reactor 28 moves to the first capacitor C1, and the voltage of the first capacitor C1 increases. This reduces the voltage imbalance between the first capacitor and the second capacitor.

In addition, in the charging device 10 according to the embodiment, the ECU 60 repeatedly switches the first switching element SB1 and the second switching element SB2 of the balancer circuit 26 on and off, thereby transferring the charge of the second capacitor C2 to the first capacitor C1, thereby eliminating the voltage imbalance between the first capacitor C1 and the second capacitor C2.

In the charging device 10 according to the embodiment, when the voltage of the second capacitor C2 exceeds the threshold value while the DC charger 30 is charging the battery 12, the balancer circuit 26 is driven to move the charge of the second capacitor C2 to the first capacitor C1, thereby preventing the voltage of the second capacitor C2 from reaching the capacitor upper limit voltage. Therefore, the charging device 10 according to the embodiment can continue charging the battery 12 without stopping the charging operation before the charging of the battery 12 is completed due to overcharging of the second capacitor C2.

REFERENCE SIGNS LIST 10 Charging device 12 Battery 16 Capacitor section 18 Inverter 20 Motor generator 22 Positive bus 24 Negative bus 26 Balancer circuit 28 Reactor 30 DC charger 32N N terminal 32P P terminal 40 Charging relay device 42N, 42P Charging relay 44P Reactor 50 Charger connection section 60 ECU
62 Charging control section 64 Gate signal generating section C1 First capacitor C2 Second capacitor DU1, DU2, DV1, DV2, DW1, DW2 Diodes SB1, SU1, SV1, SW1 First switching elements SB2, SU2, SV2, SW2 Second switching elements SU3, SV3, SW3 Third switching elements SU4, SV4, SW4 Fourth switching element

Claims (1)

a capacitor section in which a first capacitor and a second capacitor are connected in series between a positive terminal and a negative terminal of the storage battery;
a first diode having a cathode connected to a wiring connecting the first switching element and the second switching element and an anode connected to a wiring connecting the first capacitor and the second capacitor, and a second diode having an anode connected to a wiring connecting the third switching element and the fourth switching element and a cathode connected to a wiring connecting the first capacitor and the second capacitor, the power converter including a three-level inverter capable of selectively outputting a voltage of one of three different voltage values to a motor generator by turning on and off the first switching element, the second switching element, the third switching element, and the fourth switching element, respectively, for three phases, i.e., a U-phase, a V-phase, and a W-phase, the three-level inverter being connected in parallel with the storage battery;
A control device that controls switching on and off of each switching element of the power converter;
a first connection terminal electrically connected to a P terminal of a DC charger between the first switching element and the second switching element in the three-level inverter of any one of the U phase, the V phase, and the W phase;
a second connection terminal electrically connected to an N terminal of the DC charger between the third switching element and the fourth switching element in the three-level inverter of the other one of the U phase, the V phase, and the W phase;
A charging device comprising:
a balancer circuit is provided between the storage battery and the capacitor unit, the balancer circuit being connected in parallel with the storage battery and the capacitor unit, and transferring charge from the first capacitor to the second capacitor when a voltage of the first capacitor exceeds a preset threshold value;
The threshold value is a voltage lower than a capacitor upper limit voltage and higher than half a voltage of a fully charged voltage of the storage battery,
the balancer circuit is composed of a first balancer switching element, a second balancer switching element, and a reactor,
the first balancer switching element and the second balancer switching element are connected in series between a positive terminal and a negative terminal of the storage battery,
one side of the reactor is connected between the first balancer switching element and the second balancer switching element, and the other side of the reactor is connected between the first capacitor and the second capacitor;
The control device includes:
A charging device characterized in that, during charging of the storage battery by the DC charger, when the voltage of the first capacitor is higher than the voltage of the second capacitor and the voltage of the first capacitor exceeds the threshold, the first balancer switching element is turned on and the second balancer switching element is turned off, and then, at a predetermined timing when the voltage of the first capacitor falls below the threshold, the first balancer switching element is turned off and the second balancer switching element is turned on ,