Charging device

Abstract

To provide a charging device that can continue charging of a storage battery without stopping charging operation before completion of charging by overcharge by a capacitor.SOLUTION: A charging device includes a capacitor unit having a first capacitor and a second capacitor connected in series between a positive electrode side terminal and a negative electrode side terminal of a storage battery, a power converter having a three-level inverter connected in parallel to the storage battery, a control device that controls to switch on and off of each switching element, a first connection terminal connected to a P terminal of a charger between a first switching element and a second switching element of any one phase among three phases, and a second connection terminal connected to an N terminal of the charger between a third switching element and a fourth switching element of another phase. When a voltage of one capacitor becomes more than a predetermined threshold during charging of the storage battery by a DC charger, a current is supplied from the one capacitor to a motor generator.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a charging device. [Background technology]

[0002] 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 any 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 by a DC charger. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-048759 Summary of the Invention [Problem to be solved by the invention]

[0004] If the voltages of the two smoothing capacitors connected in series to the storage battery become unbalanced while the storage battery is being charged with a DC charger, the capacitors may become overcharged, and the charging operation must be stopped before the storage battery is fully charged, so there is room for improvement.

[0005] The present invention has been made in consideration of the above-mentioned problems, and its object 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. [Means for solving the problem]

[0006] In order to solve the above-mentioned problems and achieve the object, a charging device according to the present invention includes a capacitor unit 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 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, and a charging device which is a three-level inverter 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 control device for controlling 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 of the three-level inverter for any one of the U phase, the V phase, and the W phase; and a second connection terminal electrically connected to an N terminal of the DC charger between the third switching element and the fourth switching element of the three-level inverter for the other of the U phase, the V phase, and the W phase, wherein the control device controls switching on and off of each switching element of the power converter so that a current flows from the one capacitor to the motor generator when a voltage of one of the first capacitor and the second capacitor exceeds a preset threshold value during charging of the storage battery by the DC charger.

[0007] As a result, in the charging device according to the present invention, while the storage battery is being charged by the DC charger, a current is passed from the one of the capacitors that has exceeded the threshold to the motor generator, thereby lowering the voltage of the one of the capacitors. Therefore, in the charging device according to the present invention, the voltage of the one of the capacitors is prevented from reaching the capacitor upper limit voltage, The charging of the storage battery can be continued without stopping the charging operation before the charging is completed due to overcharging of the capacitor.

[0008] In addition, in the above, when current flows from one of the capacitors to the motor generator while the storage battery is being charged by the DC charger, the control device may control the on / off switching of each switching element of the power converter so that only a d-axis current flows to the motor generator.

[0009] This makes it possible to prevent the motor generator from rotating when a current is passed from one of the capacitors to the motor generator. Effect of the Invention

[0010] The charging device according to the present invention has an advantage in that it is possible to continue charging the storage battery without stopping the charging operation before the charging is completed due to overcharging of the capacitor. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a configuration diagram of a power system according to an embodiment. [Diagram 2] FIG. 2 is a block diagram showing the configuration of the power system according to the embodiment. [Diagram 3] FIG. 3 is a diagram showing the circuit state when the battery is charged by a DC charger. [Figure 4] FIG. 4 is a diagram showing voltage waveforms when a voltage imbalance occurs during charging and current is caused to flow from the first capacitor and the second capacitor to the motor generator. [Diagram 5]FIG. 5 is a diagram showing voltage waveforms when a voltage imbalance occurs during charging and current is caused to flow from the first capacitor and the second capacitor to the motor generator. [Figure 6] FIG. 6 is a vector diagram showing an example of vector synthesis for flowing a d-axis current. [Figure 7] FIG. 7 is a diagram showing how current flows from the first capacitor and the second capacitor to the motor generator, with the current vector being oriented in the direction of (1). [Figure 8] FIG. 8 is a diagram showing how current flows from the first capacitor and the second capacitor to the motor generator, with the current vector being oriented in the direction of (2). [Figure 9] FIG. 9 is a diagram showing how current flows from the first capacitor and the second capacitor to the motor generator, with the current vector being oriented in the direction of (3). [Figure 10] FIG. 10 is a diagram showing how current flows from the first capacitor and the second capacitor to the motor generator, with the current vector being oriented in the direction of (4). [Figure 11] FIG. 11 is a diagram showing how current flows from the first capacitor and the second capacitor to the motor generator, with the current vector being oriented in the direction of (5). [Figure 12] FIG. 12 is a diagram showing how current flows from the first capacitor and the second capacitor to the motor generator, with the current vector being oriented in the direction of (6). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, an embodiment of a charging device according to the present invention will be described. However, the present invention is not limited to the embodiment.

[0013] 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, plug-in hybrid electric vehicles (PHEVs), and range extended electric vehicles (REEVs).

[0014] The power system according to the embodiment is composed of a charging device 10, a motor generator 20, a DC charger 30, etc. 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.

[0015] The charging device 10 includes a battery 12, a capacitor unit 16, an inverter 18, a charging relay device 40, and an ECU (Electronic Control Unit) 60. The charging device 10 is electrically connected to a motor generator 20, and also functions as a power supply device that supplies power from the battery 12 to the motor generator 20.

[0016] 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, or the like can be used as battery 12. In addition, in FIG. 1, "VB" is the battery voltage. It is desirable that the battery voltage of battery 12 is, for example, 400 V or higher.

[0017] The capacitor unit 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 a 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 accumulate the same electric charge, the neutral point voltage, which is the voltage between the neutral point NP1 and the negative bus 24, is clamped to a voltage 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. Moreover, VC1 in FIG. 1 is the voltage across the terminals of the first capacitor C1.

[0018] The inverter 18 is composed of an upper arm to which a positive voltage, which is the voltage between a positive bus 22 and a neutral point NP1, is supplied, and a lower arm to which a negative voltage, which is the voltage between the neutral point NP1 and a 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, and it is possible to output three-level three-phase AC voltages to the motor generator 20.

[0019] In addition, inverter 18 has a U-phase arm that outputs a U-phase voltage to motor generator 20, a V-phase arm that outputs a V-phase voltage to motor generator 20, and a W-phase arm that outputs a W-phase voltage to motor generator 20.

[0020] In the U-phase arm, a first switching element SU1, a second switching element SU2, a third switching element SU3, and a fourth switching element SU4 are connected in series in this order from the positive bus 22 toward 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 such that a freewheeling diode is connected in inverse parallel to a semiconductor element. Note that the inverse 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. An 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 an 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 a cathode side connected to the intermediate point PU1 and an anode side connected to the neutral point NP1. The diode DU2 has an anode side connected to the intermediate point PU2 and a cathode side connected to the neutral point NP1. In this configuration, a U-phase voltage is output to the motor generator 20 from a connection point between the second switching element SU2 and the third switching element SU3.

[0021] 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 freewheeling diode is connected in inverse parallel to the semiconductor element. An 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 an 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 in the wiring connecting these two diodes DV1 and DV2 is connected to the neutral point NP1 of the capacitor unit 16. In other words, the diode DV1 has a cathode connected to the midpoint PV1 and an anode connected to the neutral point NP1. The diode DV2 has an anode connected to the midpoint PV2 and a cathode connected to the neutral point NP1. In this configuration, a V-phase voltage is output to the motor generator 20 from a connection point between the second switching element SV2 and the third switching element SV3.

[0022] 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 freewheeling diodes inversely parallel to the semiconductor elements. An 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 an 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 such 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 in the wiring connecting these two diodes DW1 and DW2 is connected to the neutral point NP1 of the capacitor unit 16. In other words, the diode DW1 has a cathode connected to the midpoint PW1 and an anode connected to the neutral point NP1. The diode DW2 has an anode connected to the midpoint PW2 and a cathode connected to the neutral point NP1. In this configuration, a W-phase voltage is output to the motor generator 20 from a connection point between the second switching element SW2 and the third switching element SW3.

[0023] In this embodiment, each switching element of the inverter 18 may be an IGBT (Insulated Gate Bipolar Transistor) or the like.

[0024] 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.

[0025] 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, 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. A charging relay device 40 having a charging relay 42P and a charging relay 42N, and a reactor 44P are provided between the charger connection section 50 and the inverter 18. Note that Vchg in FIG. 1 is the charger voltage.

[0026] 1, the P terminal 32P of the DC charger 30 is electrically connected to a 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. Also, the N terminal 32N of the DC charger 30 is electrically connected to a midpoint PU2 between the third switching element SU3 and the fourth switching element SU4 in the U-phase arm via a charging relay 42N.

[0027] In the charging device 10 of the embodiment, the intermediate points PU1, PV1, PW1, which are the first intermediate points in the three-level inverter of any one of the U-phase arm, V-phase arm, and W-phase arm, are connected to the P terminal 32P of the DC charger 30, and the intermediate points PU2, PV2, 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.

[0028] 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.

[0029] 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 intermediate point) 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 intermediate point) in the three-level inverter of the other phase. In addition, since the charging device 10 according to the embodiment is a method of connecting the DC charger 30 to an existing terminal that connects the motor generator 20 and the inverter 18, it is possible to realize the charging device 10 according to the embodiment without processing the inverter 18 or adding internal wiring to an existing three-level inverter having a voltage dividing capacitor, and therefore it is possible to reduce costs. In addition, since a capacitor with high withstand voltage or additional parts are not required, it is possible to reduce costs and part sizes.

[0030] 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, etc. The ECU 60 includes a charging control unit 62, a gate signal generating unit 64, etc.

[0031] 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, signals of the voltages VC1 and VC2 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 signals of the voltages VC1 and VC2 to the gate signal generating unit 64. The gate signal generating unit 64 generates a gate signal for switching on and off each switching element of the inverter 18, and outputs the generated gate signal to each switching element. The gate signal generating unit 64 also generates a gate signal for switching on and off each switching element of the balancer circuit 26, and outputs the generated gate signal to each switching element.

[0032] Fig. 3 is a diagram showing the circuit state when the battery 12 is charged by the DC charger 30. In Fig. 3, switching elements that are in the ON state are circled, and switching elements that are in the OFF state are not circled.

[0033] 3, when the battery 12 is charged by the DC charger 30, first, the ECU 60 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, and supplies DC voltage from the DC charger 30 to the battery 12 via the inverter 18, thereby charging the battery 12.

[0034] The fourth switching element SU4 and the first switching element SV1 may be turned off because current flows through their respective freewheel diodes. As a result, all switching elements of the inverter 18 are turned off, and it is not necessary to perform a switching operation for switching each switching element of the inverter 18 between on and off. This can improve charging efficiency and suppress the need for additional inverter elements and cooling mechanisms for charging. On the other hand, by turning on the fourth switching element SU4 and the first switching element SV1, it is possible to ensure durability when a current flows through the fourth switching element SU4 and the first switching element SV1. Also, since the on and off states of each switching element of the inverter 18 are fixed during charging, switching loss can be reduced.

[0035] FIG. 4 is a diagram showing voltage waveforms when a current flows from the first capacitor C1 to the motor generator 20 in the case where a voltage imbalance occurs during charging.

[0036] 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. When the voltage of one of the capacitors reaches the capacitor upper limit voltage in this way, it is necessary to stop charging the battery 12 even though charging is not complete.

[0037] FIG. 5 is a diagram showing voltage waveforms when a voltage imbalance occurs during charging and a current is caused to flow from the first capacitor C1 to the motor generator 20. In FIG.

[0038] 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 ECU 60 switches on and off each switching element of the inverter 18 to control the flow of current from the one of the capacitors to the motor generator 20. The threshold is set to a voltage lower than a preset capacitor upper limit voltage so as to prevent the first capacitor C1 and the second capacitor C2 from being damaged.

[0039] 5, when the first capacitor C1 exceeds the threshold due to a voltage imbalance between the first capacitor C1 and the second capacitor C2, the ECU 60 switches on and off each switching element of the inverter 18 to cause a current to flow from the first capacitor C1 to the motor generator 20, thereby discharging the first capacitor C1 to lower the voltage and preventing the voltage of the first capacitor C1 from reaching the battery upper limit voltage. After the first capacitor C1 is discharged to lower the voltage, the first capacitor C1 and the second capacitor C2 are charged by the battery 12.

[0040] In the charging device 10 of the embodiment, when the first capacitor C1 exceeds the threshold value while the battery 12 is being charged by the DC charger 30, current is passed from the first capacitor C1 to the motor generator 20, thereby making it possible to 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.

[0041] Furthermore, when the voltage of the second capacitor C2 exceeds the threshold value due to a voltage imbalance between the first capacitor C1 and the second capacitor C2, the ECU 60 switches on and off each switching element of the inverter 18 to cause a current to flow from the second capacitor C2 to the motor generator 20, thereby discharging the second capacitor C2 and lowering the voltage, so that the voltage of the second capacitor C2 does not reach the battery upper limit voltage. After the second capacitor C2 is discharged and the voltage is lowered, the first capacitor C1 and the second capacitor C2 are charged by the battery 12.

[0042] In the charging device 10 of the embodiment, when the second capacitor C2 exceeds the threshold value while the battery 12 is being charged by the DC charger 30, current is passed from the second capacitor C2 to the motor generator 20, thereby making it possible to 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.

[0043] In the charging device 10 according to the embodiment, as shown in FIG. 5, the first capacitor C1 and the second capacitor C2 are discharged after charging of the battery 12 is completed.

[0044] Here, in the charging device 10 of the embodiment, when current flows from the first capacitor C1 and the second capacitor C2 to the motor generator 20 while the battery 12 is being charged by the DC charger 30, control is performed so that only the d-axis current flows through the motor generator 20 in order to prevent the motor generator 20 from rotating.

[0045] Next, a method of controlling so that only the d-axis current flows from each of the first capacitor C1 and the second capacitor C2 to the motor generator 20 will be described.

[0046] Fig. 6 is a vector diagram showing an example of vector synthesis for flowing a d-axis current. In Fig. 6, the directions of (1), (3), and (5) correspond to the +U-axis direction, +V-axis direction, and +W-axis direction, respectively, and the directions of (4), (6), and (2) correspond to the -U-axis direction, -V-axis direction, and -W-axis direction, respectively. In the example shown in Fig. 6, the d-axis current is flowed by combining a current vector in the direction of (1) and a current vector in the direction of (2), in the same way as the general PWM concept.

[0047] FIG. 7 is a diagram showing how current flows from the first capacitor C1 and the second capacitor C2 to the motor generator 20, which are current vectors in the direction of (1). FIG. 8 is a diagram showing how current flows from the first capacitor C1 and the second capacitor C2 to the motor generator 20, which are current vectors in the direction of (2). FIG. 9 is a diagram showing how current flows from the first capacitor C1 and the second capacitor C2 to the motor generator 20, which are current vectors in the direction of (3). FIG. 10 is a diagram showing how current flows from the first capacitor C1 and the second capacitor C2 to the motor generator 20, which are current vectors in the direction of (4). FIG. 11 is a diagram showing how current flows from the first capacitor C1 and the second capacitor C2 to the motor generator 20, which are current vectors in the direction of (5). FIG. 12 is a diagram showing how current flows from the first capacitor C1 and the second capacitor C2 to the motor generator 20, which are current vectors in the direction of (6).

[0048] In the charging device 10 according to the embodiment, as shown in Fig. 7 to Fig. 12, by controlling the on / off switching of each switching element of the inverter 18, it is possible to pass a current in any phase of the motor generator 20, in other words, in any direction of (1) to (6) in the figures. Therefore, in the charging device 10 according to the embodiment, when a current is passed from the first capacitor C1 and the second capacitor C2 to the coil of the motor generator 20 during charging of the battery 12 by the DC charger 30, it is possible to combine current vectors in any direction of (1) to (6) above to pass only a d-axis current without passing a q-axis current to the motor generator 20 so that the torque of the motor generator 20 is not generated. This makes it possible to prevent the motor generator 20 from rotating when a current is passed from the first capacitor C1 and the second capacitor C2 to the motor generator 20. [Explanation of symbols]

[0049] 10 Charging device 12 Battery 16 Capacitor section 18 Inverter 20 Motor generator 22 Positive busbar 24 negative bus 30 DC charger 32N N terminal 32P P terminal 40 Charging relay device 42N, 42P Charging relay 44P Reactor 50 Charger connector 60 ECU 62 Charging control unit 64 Gate signal generator C1 First capacitor C2 Second capacitor DU1,DU2,DV1,DV2,DW1,DW2 Diodes SU1, SV1, SW1 First switching element SU2, SV2, SW2 Second switching element SU3, SV3, SW3 Third switching element SU4, SV4, SW4 4th 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: The charging device is characterized in that the control device controls the on / off switching of each switching element of the power converter so as to flow current from the first capacitor or the second capacitor to the motor generator when the voltage of one of the first capacitor and the second capacitor exceeds a predetermined threshold while the storage battery is being charged by the DC charger.

2. 2. The charging device according to claim 1, wherein the control device controls the on / off switching of each switching element of the power converter so that only a d-axis current flows to the motor generator when a current flows from one of the capacitors to the motor generator while the storage battery is being charged by the DC charger.

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