Power conversion device

Abstract

A power conversion device, suitable for a system including a battery (20) and an electrical device (51), includes a three-level inverter (30) and a rotating electrical machine (10) having windings (13U, 13V, 13W). A three-level inverter is provided with a first power storage unit (21), a second power storage unit (22), and switches (SUH-SWL, QU-QW, Su1-Sw4). The positive electrode side of the first power storage unit is connected to the positive electrode terminal of the storage battery, and the negative electrode side of the second power storage unit is connected to the negative electrode terminal of the storage battery. This power conversion device is provided with: a connection unit (35, 62) that connects an electrical device and a three-level inverter, and that can be electrically connected to a storage battery via a neutral point between the negative electrode side of a first power storage unit and the positive electrode side of a second power storage unit; and a control unit (40) that, in a state in which the three-level inverter and the electrical device are connected via the connection unit, performs switching control of each switch so as to transmit power between the electrical device and the battery.

Description

Citation of related applications

[0001] This application is based on Japanese Patent Application No. 2022-110235 filed on July 8, 2022, and the contents thereof are incorporated herein by reference. Technical Field

[0002] The present disclosure relates to a power conversion device including a three-level inverter and a rotating electric machine having a winding electrically connected to the three-level inverter. Background Art

[0003] As such a power conversion device, a charging control system suitable for charging a battery of an electric vehicle from an external charger is known, as described in Patent Document 1. In this charging control system, a three-level inverter is used as an inverter constituting the power conversion device to achieve leakage current reduction and the like. Prior art literature Patent Literature

[0004] Patent Document 1: Japanese Patent No. 6347453 Summary of the invention

[0005] A power conversion device is sometimes used in a system including a battery and an electrical device electrically connected to the battery. For example, when a battery is installed in a vehicle such as an electric car, the charging capacity of the battery may become large. In this case, since the terminal voltage of the battery is high, various requirements may be placed on the system when driving the electrical device. A structure for responding to these requirements is added to the power conversion device, and the power conversion device may become larger.

[0006] The present disclosure has been made in view of the above-mentioned technical problems, and a main object of the present disclosure is to provide a power conversion device that can be miniaturized.

[0007] The present invention discloses a power conversion device, which is applicable to a system including a storage battery and an electrical device that can be electrically connected to the storage battery. The power conversion device includes: a three-level inverter, which is electrically connected to the storage battery; and a rotating electric machine, which has a winding electrically connected to the three-level inverter, and the three-level inverter has: a first storage unit and a second storage unit connected in series; and a switch, which connects the winding to a neutral point between a positive electrode side of the first storage unit, a negative electrode side of the first storage unit and a positive electrode side of the second storage unit, and and any one of the negative sides of the above-mentioned second power storage unit, the positive side of the above-mentioned first power storage unit is connected to the positive terminal of the above-mentioned battery, and the negative side of the above-mentioned second power storage unit is connected to the negative terminal of the above-mentioned battery, the above-mentioned power conversion device includes: a connecting part, the above-mentioned connecting part connects the above-mentioned electrical equipment with the above-mentioned three-level inverter, and can be electrically connected to the above-mentioned battery via the above-mentioned neutral point; and a control part, the above-mentioned control part controls the switching of each of the above-mentioned switches in a state where the above-mentioned three-level inverter and the above-mentioned electrical equipment are connected via the above-mentioned connecting part, so as to transmit power between the above-mentioned electrical equipment and the above-mentioned battery.

[0008] According to the present disclosure, the electrical device is connected to the three-level inverter through the connection part, and the electrical device is electrically connected to the battery via the neutral point. In the state where the electrical device and the three-level inverter are connected via the neutral point, the switch control of each switch is performed. By performing the switch control, the requirements for the system can be met without setting a dedicated circuit in the power conversion device. As a result, the miniaturization of the power conversion device can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The above objects, other objects, features and advantages of the present disclosure will become more apparent with reference to the accompanying drawings and the following detailed description. Figure 1 It is a configuration diagram of a motor control system according to the first embodiment. Figure 2 It is a diagram showing the connection method of the high-voltage charger. Figure 3 It is a diagram showing an example of voltage boost control. Figure 4 It is a diagram showing an example of voltage boost control. Figure 5 is a block diagram showing boost control. Figure 6 It is a configuration diagram of a motor control system according to a second embodiment. Figure 7 It is a diagram showing an example of voltage boost control. Figure 8 It is a diagram showing an example of voltage boost control. Fig. 9 It is a configuration diagram of a motor control system according to another embodiment. DETAILED DESCRIPTION

[0010] <First embodiment> Hereinafter, a first embodiment of a power conversion device according to the present disclosure will be described with reference to the drawings. In this embodiment, the power conversion device is mounted on a vehicle such as an electric car. like Figure 1 As shown, the motor control system is installed in a vehicle, and includes a rotating motor 10, a battery 20, an inverter 30, and a control device 40. The rotating motor 10 is a vehicle-mounted main machine, and its rotor 11 can transmit power to the driving wheel 12 of the vehicle. In the present embodiment, the rotating motor 10 is a three-phase synchronous machine, and as a stator winding, it includes a U-phase winding 13U, a V-phase winding 13V, and a W-phase winding 13W connected in star connection. The windings 13U, 13V, and 13W of each phase are arranged in a manner that each is staggered by 120° in electrical angle. The rotating motor 10 is, for example, a permanent magnet synchronous machine. In the present embodiment, the rotating motor 10 and the inverter 30 are equivalent to a "power conversion device".

[0012] The rotating shaft of the rotor 11 and the axle of the driving wheel 12 are connected via a power transmission mechanism 14. Specifically, the power transmission mechanism 14 includes at least one of a clutch and a transmission. The clutch has the function of switching the connection and separation between the input shaft of the clutch and the output shaft of the clutch, and adjusting the degree of transmission of the torque transmitted from the rotor 11 to the axle of the driving wheel 12. The clutch is, for example, a hydraulically driven wet clutch. The transmission has the function of adjusting the speed ratio, which is the ratio of the rotation speed of the input shaft of the transmission to the rotation speed of the output shaft of the transmission. The transmission is, for example, a CVT (continuously variable transmission) or a stepped transmission.

[0013] The battery 20 is electrically connected to the rotating electrical machine 10 via the inverter 30. In the present embodiment, the battery 20 is configured as a battery pack including battery cells connected in series, for example. As the battery cell, for example, a secondary battery such as a lithium ion battery can be used. The terminal voltage VH of the battery 20 is, for example, 600 to 800V.

[0014] The inverter 30 is a power conversion circuit that converts the DC power supplied from the battery 20 into three-phase AC power by switch control, and supplies the converted AC power to the rotating electric machine 10. A first capacitor 21 as a "first power storage unit" and a second capacitor 22 as a "second power storage unit" are provided on the battery 20 side of the inverter 30. The first capacitor 21 and the second capacitor 22 are connected in series. The series connection of the first capacitor 21 and the second capacitor 22 is connected in parallel to the battery 20. In the present embodiment, the electrostatic capacitance of the first capacitor 21 and the electrostatic capacitance of the second capacitor 22 are the same value. In addition, the first capacitor 21 and the second capacitor 22 can be provided outside the inverter 30, or can be built into the inverter 30.

[0015] In the present embodiment, the inverter 30 is a T-type three-level inverter. The inverter 30 includes a series connection of three corresponding upper arm switches SUH, SVH, SWH and lower arm switches SUL, SVL, SWL. As each switch SUH~SWL, a voltage-controlled semiconductor switch element is used, specifically, an N-channel MOSFET is used. Therefore, the high potential side terminal of each switch SUH~SWL is the drain, and the low potential side terminal is the source. Each switch SUH, SVH, SWH, SUL, SVL, SWL has a corresponding body diode DUH, DVH, DWH, DUL, DVL, DWL.

[0016] The source of the U-phase upper arm switch SUH is connected to the drain of the U-phase lower arm switch SUL. The connection point between the U-phase upper arm switch SUH and the U-phase lower arm switch SUL is connected to the input terminal of the U-phase of the rotating electrical machine 10. The source of the V-phase upper arm switch SVH is connected to the drain of the V-phase lower arm switch SVL. The connection point between the V-phase upper arm switch SVH and the V-phase lower arm switch SVL is connected to the input terminal of the V-phase of the rotating electrical machine 10. The source of the W-phase upper arm switch SWH is connected to the drain of the W-phase lower arm switch SWL. The connection point between the W-phase upper arm switch SWH and the W-phase lower arm switch SWL is connected to the input terminal of the W-phase of the rotating electrical machine 10.

[0017] The drain of each upper arm switch SUH to SWH is connected through a positive-side bus bar 31 such as a bus bar. The positive-side bus bar 31 is connected to the positive terminal of the battery 20 and the first end of the first capacitor 21. The second end of the first capacitor 21 is connected to the first end of the second capacitor 22 via the neutral point O. The source of each lower arm switch SUL to SWL is connected through a negative-side bus bar 32 such as a bus bar. The negative-side bus bar 32 is connected to the negative terminal of the battery 20 and the second end of the second capacitor 22.

[0018] The inverter 30 includes clamp switches QU, QV, and QW that conduct and cut off bidirectional current. In the present embodiment, as switches constituting each clamp switch QU to QW, voltage-controlled semiconductor switch elements, specifically, N-channel MOSFETs, are used. Each switch constituting each clamp switch QU to QW has a corresponding body diode DU, DV, and DW.

[0019] Specifically, the sources of the switches constituting the U-phase clamp switch QU are connected to each other. The drain of one of the switches constituting the U-phase clamp switch QU is connected to the connection point of the U-phase upper arm switch SUH and the U-phase lower arm switch SUL, and the drain of the other is connected to the neutral point O. The sources of the switches constituting the V-phase clamp switch QV are connected to each other. The drain of one of the switches constituting the V-phase clamp switch QV is connected to the connection point of the V-phase upper arm switch SVH and the V-phase lower arm switch SVL, and the drain of the other is connected to the neutral point. The sources of the switches constituting the W-phase clamp switch QW are connected to each other. The drain of one of the switches constituting the W-phase clamp switch QW is connected to the connection point of the W-phase upper arm switch SWH and the W-phase lower arm switch SWL, and the drain of the other is connected to the neutral point O.

[0020] The motor control system includes a phase current sensor 41 and a rotation angle sensor 42. The phase current sensor 41 detects the U, V, and W phase currents I uvw flowing through the rotating electrical machine 10. In addition, the phase current sensor 41 only needs to detect the currents of at least two phases among the three-phase currents. The rotation angle sensor 42 is, for example, a resolver, and detects the electrical angle θe of the rotating electrical machine 10. The detection values ​​of the sensors 41 and 42 are input to the control device 40.

[0021] The control device 40 implements various control functions by executing programs stored in a storage device included in the control device 40. The various control functions may be implemented by an electronic circuit as hardware or by both hardware and software.

[0022] The control device 40 performs switching control of the switches SUH to SWL, QU to QW. As the switching control, the control device 40 performs motor drive control for feedback-controlling the control amount of the rotary electric machine 10 to its command value. The control amount of the motor drive control is, for example, torque.

[0023] An external charger is provided outside the vehicle for charging the battery 20. The external charger is, for example, a stationary charger, and is also called a quick charger.

[0024] The inverter 30 is configured to be connected to an external charger. In the present embodiment, the inverter 30 is configured to be connected to a high-voltage charger 50 or a low-voltage charger 51. The charging voltage of the high-voltage charger 50 is the same as the rated voltage of the battery 20, for example, 600V to 800V. The charging voltage of the low-voltage charger 51 is lower than the rated voltage of the battery 20, for example, 400V. In other words, the battery 20 is a large-capacity battery that can be charged to a voltage higher than the charging voltage of the low-voltage charger 51. In the present embodiment, the low-voltage charger 51 is equivalent to an "electrical device".

[0025] As a power interface for supplying power from an external charger to the battery 20, the inverter 30 includes a positive-side connection portion 60 and a negative-side connection portion 61. The positive terminal of the battery 20 is connected to the positive-side connection portion 60 via the positive-side wiring 33. A positive-side switch T1 is provided in the positive-side wiring 33. The negative terminal of the battery 20 is connected to the negative-side connection portion 61 via the negative-side wiring 34. A negative-side switch T2 is provided in the negative-side wiring 34. Each switch T1, T2 is a switch for switching on and off the current flowing from the external charger to the battery 20, and is, for example, a mechanical relay or a semiconductor switching element. Each switch T1, T2 is turned on and off by the control device 40.

[0026] Here, the control of charging the battery 20 by the high-voltage charger 50 will be described. Figure 2 As shown, the positive terminal 50a of the high-voltage charger 50 is connected to the positive terminal of the battery 20 via the positive connection portion 60, the positive wiring 33, and the positive switch T1. In addition, the negative terminal 50b of the high-voltage charger 50 is connected to the negative terminal of the battery 20 via the negative connection portion 61, the negative wiring 34, and the negative switch T2. Thus, the high-voltage charger 50 is electrically connected to the battery 20.

[0027] Specifically, a user (e.g., a driver) or an operator of a vehicle connects a connection plug composed of a positive terminal 50a and a negative terminal 50b of a high-voltage charger 50 to a high-voltage charging inlet composed of a positive connection portion 60 and a negative connection portion 61. When the connection plug of the high-voltage charger 50 is connected to the high-voltage charging inlet, a pilot signal (Japanese: pilot signal) CP is generated by the high-voltage charger 50 and input to the control device 40 via the high-voltage charging inlet. The pilot signal CP is a signal including information indicating whether the connection plug of the high-voltage charger 50 and the high-voltage charging inlet are connected. The control device 40 determines whether the connection plug of the high-voltage charger 50 and the high-voltage charging inlet are connected based on the pilot signal CP. When the control device 40 determines that the connection plug of the high-voltage charger 50 is connected to the high-voltage charging inlet, the positive switch T1 and the negative switch T2 are turned on. As a result, the high-voltage charger 50 is electrically connected to the battery 20, and the high-voltage charger 50 charges the battery 20.

[0028] Next, the control of charging the battery 20 by the low-voltage charger 51 instead of the high-voltage charger 50 is described. The low-voltage charger 51 is an external charger whose charging voltage is lower than the rated voltage of the battery 20. In this case, since the rated voltage of the battery 20 is higher than the charging voltage of the low-voltage charger 51, when the battery 20 is charged by the low-voltage charger 51, it is necessary to boost the charging voltage of the low-voltage charger 51. Here, it is conceivable to add a boost circuit for boosting the charging voltage of the low-voltage charger 51 to the power conversion device. However, in this case, the power conversion device may be enlarged.

[0029] In addition, unlike the present embodiment, in the structure of the comparative example including the connection path connecting the neutral point of the star-connected multi-phase winding to the low-voltage charger, it is possible to consider allowing the current to flow from the low-voltage charger to the battery via each phase winding, the inverter, and the connection path. Thus, the rotating electrical machine and the inverter can be used as a boost circuit for boosting the charging voltage of the low-voltage charger. However, in this case, it is necessary to add a structure for connecting the neutral point of each phase winding to the low-voltage charger, and the manufacturing cost of the power conversion device may increase.

[0030] Therefore, in this embodiment, if Figure 1As shown, the inverter 30 has a neutral point connection portion 62 as a power interface for supplying power from the low voltage charger 51 to the storage battery 20. The neutral point O is connected to the neutral point connection portion 62 via the neutral point wiring 35. A neutral point switch T3 is provided in the neutral point wiring 35. The neutral point switch T3 is a switch for switching on and off the current flowing from the low voltage charger 51 to the neutral point O, and is, for example, a mechanical relay or a semiconductor switch element. The neutral point switch T3 is turned on and off by the control device 40.

[0031] like Figure 3 and Figure 4 As shown, the positive terminal 51a of the low voltage charger 51 is connected to the neutral point O via the neutral point connection portion 62, the neutral point wiring 35 and the neutral point switch T3. In addition, the negative terminal 51b of the low voltage charger 51 is connected to the negative terminal of the battery 20 via the negative side connection portion 61, the negative side wiring 34 and the negative side switch T2. Thus, the low voltage charger 51 is electrically connected to the battery 20 via the neutral point O.

[0032] Specifically, the user or operator of the vehicle connects the connection plug composed of the positive terminal 51a and the negative terminal 51b of the low-voltage charger 51 to the low-voltage charging inlet composed of the negative-side connection portion 61 and the neutral point connection portion 62. When the connection plug of the low-voltage charger 51 is connected to the low-voltage charging inlet, the pilot signal CP is generated by the low-voltage charger 51 and input to the control device 40 via the low-voltage charging inlet. The pilot signal CP is a signal including information indicating whether the connection plug of the low-voltage charger 51 and the low-voltage charging inlet are connected. The control device 40 determines whether the connection plug of the low-voltage charger 51 and the low-voltage charging inlet are connected based on the pilot signal CP. When the control device 40 determines that the connection plug of the low-voltage charger 51 is connected to the low-voltage charging inlet, the negative-side switch T2 and the neutral point switch T3 are turned on. As a result, the low-voltage charger 51 is electrically connected to the battery 20 via the neutral point O.

[0033] The control device 40, while being connected to the inverter 30 and the low-voltage charger 51 via the negative-side connection portion 61 and the neutral-point connection portion 62, performs a voltage-boosting control for boosting the charging voltage of the low-voltage charger 51 by passing a current through the rotating electric machine 10 and the inverter 30, and supplies the boosted voltage to the battery 20. The voltage-boosting control will be described in detail below.

[0034] As a step-up control, the control device 40 turns off the clamp switch in a specific phase that is a part of each phase, and turns on the upper arm switch and the lower arm switch in the specific phase alternately. In addition, the control device 40 turns off the upper arm switch and the lower arm switch of the phase other than the specific phase in each phase, and turns on the clamp switch of the phase other than the specific phase. Figure 3and Figure 4 The current path in the voltage boost control when the specific phase is the W phase is shown.

[0035] When the specific phase is the W phase, during the implementation of the boost control, the U-phase upper arm switch SUH, the V-phase upper arm switch SVH, the U-phase lower arm switch SUL, the V-phase lower arm switch SVL, and the W-phase clamp switch QW are turned off, and the U-phase clamp switch QU and the V-phase clamp switch QV are turned on. In addition, the W-phase upper arm switch SWH and the W-phase lower arm switch SWL are alternately turned on.

[0036] Figure 3 The current path when the W-phase upper arm switch SWH is turned off and the W-phase lower arm switch SWL is turned on is shown. In this case, a closed loop is formed including the low-voltage charger 51, the neutral point connection part 62, the neutral point switch T3, the U-phase clamp switch QU and the V-phase clamp switch QV, the respective phase windings 13U, 13V, 13W, the W-phase lower arm switch SWL, the negative-side busbar 32, the negative-side switch T2, and the negative-side connection part 61. As a result, magnetic energy is accumulated in the respective phase windings 13U, 13V, 13W.

[0037] Figure 4 The current path when the W-phase upper arm switch SWH is turned on and the W-phase lower arm switch SWL is turned off is shown. In this case, a closed loop is formed including the low-voltage charger 51, the neutral point connection part 62, the neutral point switch T3, the U-phase clamp switch QU and the V-phase clamp switch QV, the phase windings 13U, 13V, 13W, the W-phase upper arm switch SWH, the positive-side bus 31, the battery 20, the negative-side switch T2, and the negative-side connection part 61. As a result, the charging voltage of the low-voltage charger 51 is boosted, and the boosted voltage is supplied to the battery 20.

[0038] In addition, the specific phase may be a phase other than the W phase. When the specific phase is the U phase, as long as the V-phase upper arm switch SVH, the W-phase upper arm switch SWH, the V-phase lower arm switch SVL, the W-phase lower arm switch SWL, and the U-phase clamp switch QU are disconnected, the V-phase clamp switch QV and the W-phase clamp switch QW are connected, and the U-phase upper arm switch SUH and the U-phase lower arm switch SUL are alternately connected. When the specific phase is the V phase, as long as the U-phase upper arm switch SUH, the W-phase upper arm switch SWH, the U-phase lower arm switch SUL, the W-phase lower arm switch SWL, and the V-phase clamp switch QV are disconnected, the U-phase clamp switch QU and the W-phase clamp switch QW are connected, and the V-phase upper arm switch SVH and the V-phase lower arm switch SVL are alternately connected.

[0039] When the specific phase is the U phase or the V phase, as long as the W phase upper arm switch SWH and the W phase lower arm switch SWL, as well as the U phase clamp switch QU and the V phase clamp switch QV are disconnected, the W phase clamp switch QW is connected, and the U phase upper arm switch SUH, the V phase upper arm switch SVH, the U phase lower arm switch SUL, and the V phase lower arm switch SVL are alternately connected. When the specific phase is the V phase or the W phase, as long as the U phase upper arm switch SUH and the U phase lower arm switch SUL, as well as the V phase clamp switch QV and the W phase clamp switch QW are disconnected, the U phase clamp switch QU is connected, and the V phase upper arm switch SVH, the W phase upper arm switch SWH, the V phase lower arm switch SVL, and the W phase lower arm switch SWL are alternately connected. When the specific phases are U phase and W phase, as long as the V-phase upper arm switch SVH and the V-phase lower arm switch SVL as well as the U-phase clamp switch QU and the W-phase clamp switch QW are disconnected, the V-phase clamp switch QV is turned on, and the U-phase upper arm switch SUH, the W-phase upper arm switch SWH, the U-phase lower arm switch SUL, and the W-phase lower arm switch SWL are alternately turned on.

[0040] As the voltage step-up control, the control device 40 controls the inverter 30 and each phase winding 13U, 13V, 13W so that the q-axis current becomes zero. Figure 5 The boost control will be described below.

[0041] The control device 40 includes a command value setting unit 70. The command value setting unit 70 sets the value of the q-axis command current I q* of the d-axis command current I d* and the q-axis command current I q* in the two-phase rotating coordinate system (dq coordinate system) to 0. In the present embodiment, the command value setting unit 70 acquires the pilot signal CP input via the low-voltage charging inlet. The command value setting unit 70 determines whether the connection plug of the low-voltage charger 51 and the low-voltage charging inlet are connected based on the acquired pilot signal CP. When the command value setting unit 70 determines that the connection plug of the low-voltage charger 51 is connected to the low-voltage charging inlet, the command value setting unit 70 sets the value of the q-axis command current I q* to 0.

[0042] In addition, the command value setting unit 70 may also variably set the d-axis command current I d* based on the pilot signal CP inputted via the low-voltage charging inlet. For example, the command value setting unit 70 may also identify the rated current value of the low-voltage charger 51 based on the acquired pilot signal CP. In this case, the command value setting unit 70 may also set the d-axis command current I d* to be larger when the rated current value of the low-voltage charger 51 is larger than when the rated current value of the low-voltage charger 51 is smaller. Thus, the power supplied to the battery 20 can be increased by the boost control according to the rated current value of the low-voltage charger 51.

[0043] The control device 40 includes a three-phase conversion unit 71. The d-axis command current I d* and the q-axis command current I q* are input to the three-phase conversion unit 71. The three-phase conversion unit 71 converts the d-axis command current I d* and the q-axis command current I q* into U-, V-, and W-phase command currents I uvw* in a three-phase fixed coordinate system based on the electrical angle θe. In addition, as the electrical angle θe, the detection value of the rotation angle sensor 42 can be used.

[0044] The control device 40 includes a deviation calculation unit 72. The U, V, W phase command current I uvw* and the U, V, W phase current I uvw are input to the deviation calculation unit 72. The deviation calculation unit 72 calculates the U phase current deviation as a value obtained by subtracting the U phase current from the U phase command current. The deviation calculation unit 72 calculates the V phase current deviation as a value obtained by subtracting the V phase current from the V phase command current. The deviation calculation unit 72 calculates the W phase current deviation as a value obtained by subtracting the W phase current from the W phase command current. In addition, as the U, V, W phase current I uvw, it is sufficient to use the detection value of the phase current sensor.

[0045] The control device 40 includes a feedback control unit 73. The U, V, and W phase current deviations are input to the feedback control unit 73. The feedback control unit 73 calculates the U, V, and W phase command voltages Vuvw based on the U, V, and W phase current deviations as an operation amount for feedback-controlling the U, V, and W phase currents I uvw to U, V, and W phase command currents I uvw*. In addition, the above-mentioned feedback control may be, for example, proportional integral control.

[0046] The control device 40 includes a modulation unit 74. The U, V, and W phase command voltages Vuvw are input to the modulation unit 74. The modulation unit 74 generates operation signals for the switches SUH to SWL, QU to QW of the inverter 30 based on the comparison of the U, V, and W phase command voltages Vuvw with the carrier signal. The carrier signal is, for example, a triangular wave signal. The above-mentioned boost control is performed by turning on and off the switches SUH to SWL, QU to QW based on the operation signal. As a result, a part of each phase becomes a specific phase, and in the specific phase, the clamp switch is turned off, and the upper arm switch and the lower arm switch are alternately turned on. In addition, in the phases other than the specific phases in each phase, the upper arm switch and the lower arm switch are turned off, and the clamp switch is turned on.

[0047] In addition, in this embodiment, as Figure 5The specific phase is determined as a result of the boost control shown. Here, the specific phase is not limited to being constant during the implementation of the boost control, and may sometimes be variable. For example, there is a case where an operation signal is generated in such a way that the U phase becomes the specific phase during half of a switching cycle of the boost control, and an operation signal is generated in such a way that the U and V phases become the specific phases during the remaining period. In the implementation of the boost control, the specific phase is variable because, depending on the position of the rotor 11, if an operation signal is generated to fix the specific phase to the U phase, V phase, W phase or U phase, V phase or V phase, W phase or U phase, W phase, the q-axis current may not become 0.

[0048] According to the present embodiment described in detail above, the following effects can be obtained.

[0049] The neutral point O and the positive terminal 51a of the low-voltage charger 51 are connected via the neutral point connection portion 62. In addition, the negative terminal of the battery 20 and the negative terminal 51b of the low-voltage charger 51 are connected via the negative terminal connection portion 61. In this case, the battery 20 and the low-voltage charger 51 are electrically connected via the neutral point O. In a state where the battery 20 and the low-voltage charger 51 are electrically connected via the negative terminal connection portion 61 and the neutral point connection portion 62, the voltage step-up control is performed. That is, the voltage step-up control is performed using the phase windings 13U, 13V, 13W of the rotating electric machine 10 and the inverter 30. Therefore, without adding a dedicated circuit for stepping up the charging voltage of the low-voltage charger 51 to the power conversion device, the charging voltage of the low-voltage charger 51 can be stepped up using the inverter 30 for vehicle travel and the rotating electric machine 10, and the battery 20 can be charged by the low-voltage charger 51. As a result, the power conversion device can be miniaturized.

[0050] The voltage step-up control can be performed using the phase windings 13U, 13V, 13W of the rotating electrical machine 10 and the inverter 30 without changing the structure of the rotating electrical machine 10. Therefore, the power conversion device can be made into a simple structure compared with the structure of the comparative example in which the neutral point of each phase winding of the star connection is connected to the low voltage charger. As a result, the increase in the manufacturing cost of the power conversion device can be suppressed.

[0051] When it is determined that the positive terminal 51a of the low voltage charger 51 is connected to the neutral point connection portion 62 and the negative terminal 51b of the low voltage charger 51 is connected to the negative connection portion 61, the q-axis command current Iq* is set to 0. Thus, the rotation of the rotor 11 of the rotary electric machine 10 can be suppressed during the voltage step-up control.

[0052] Since the structure for connecting the high-voltage charger 50 and the low-voltage charger 51 to the inverter 30 is added, the power conversion device may be enlarged. In view of this, according to the present embodiment, the positive terminal 50a of the high-voltage charger 50 is connected to the positive terminal of the battery 20 via the positive terminal connection portion 60, and the negative terminal 50b of the high-voltage charger 50 is connected to the negative terminal of the battery 20 via the negative terminal connection portion 61. In addition, the positive terminal 51a of the low-voltage charger 51 is connected to the neutral point O via the neutral point connection portion 62, and the negative terminal 51b of the low-voltage charger 51 is connected to the negative terminal of the battery 20 via the negative terminal connection portion 61. That is, the structure for connecting the negative terminal 50b of the high-voltage charger 50 and the negative terminal 51b of the low-voltage charger 51 to the inverter 30 is common. Therefore, compared with the case where the negative terminal 50b of the high-voltage charger 50 and the negative terminal 51b of the low-voltage charger 51 are connected to the inverter 30 separately, the addition of a structure for connecting the negative terminal 51b of the low-voltage charger 51 to the inverter 30 can be suppressed.

[0053] <Second embodiment> Hereinafter, the second embodiment will be described with reference to the drawings, focusing on the differences from the first embodiment. In this embodiment, the structure of the inverter is changed.

[0054] like Figure 6 As shown, the motor control system includes an inverter 30a. The inverter 30a is a three-level inverter of a neutral point clamped type. The inverter 30a includes a U-phase first switch Su1 to a fourth switch Su4, a V-phase first switch Sv1 to a fourth switch Sv4, a W-phase first switch Sw1 to a fourth switch Sw4, and a first clamping diode Dc1 to a sixth clamping diode Dc6. In the present embodiment, as each switch Su1 to Su4, Sv1 to Sv4, Sw1 to Sw4, a voltage-controlled semiconductor switching element, more specifically, an IGBT is used. In this case, the high potential side terminal of the switches Su1 to Su4, Sv1 to Sv4, Sw1 to Sw4 is the collector, and the low potential side terminal is the emitter. In addition, in Figure 6 For the sake of convenience, Figure 1 The same structures are denoted by the same symbols.

[0055] The U-phase first switch Su1 to the U-phase fourth switch Su4 are connected in series in the form of connecting the emitter and the collector. The positive terminal of the battery 20 is connected to the collector of the U-phase first switch Su1 via the positive-side bus 31, and the negative terminal of the battery 20 is connected to the emitter of the U-phase fourth switch Su4 via the negative-side bus 32. The input terminal of the U-phase of the rotating electrical machine 10 is connected to the connection point of the U-phase second switch Su2 and the U-phase third switch Su3. In addition, the cathode of the first clamping diode Dc1 is connected to the connection point of the U-phase first switch Su1 and the U-phase second switch Su2, and the cathode of the second clamping diode Dc2 is connected to the anode of the first clamping diode Dc1. The connection point of the U-phase third switch Su3 and the U-phase fourth switch Su4 is connected to the anode of the second clamping diode Dc2. In addition, the freewheeling diodes Du1, Du2, Du3, and Du4 are connected in reverse parallel to the U-phase switches Su1, Su2, Su3, and Su4.

[0056] The V-phase first switch Sv1 to the V-phase fourth switch Sv4 are connected in series in the form of connecting the emitter and the collector. The positive terminal of the battery 20 is connected to the collector of the V-phase first switch Sv1 via the positive-side bus 31, and the negative terminal of the battery 20 is connected to the emitter of the V-phase fourth switch Sv4 via the negative-side bus 32. The V-phase input terminal of the rotating electric machine 10 is connected to the connection point between the V-phase second switch Sv2 and the V-phase third switch Sv3. In addition, the cathode of the third clamping diode Dc3 is connected to the connection point between the V-phase first switch Sv1 and the V-phase second switch Sv2, and the cathode of the fourth clamping diode Dc4 is connected to the anode of the third clamping diode Dc3. The connection point of the V-phase third switch Sv3 and the V-phase fourth switch Sv4 is connected to the anode of the fourth clamping diode Dc4. In addition, the freewheeling diodes Dv1, Dv2, Dv3, and Dv4 are connected in antiparallel to the switches Sv1, Sv2, Sv3, and Sv4 of the V phase.

[0057] The W-phase first switch Sw1 to the fourth switch Sw4 are connected in series in the form of connecting the emitter and the collector. The positive terminal of the battery 20 is connected to the collector of the W-phase first switch Sw1 via the positive-side bus 31, and the negative terminal of the battery 20 is connected to the emitter of the W-phase fourth switch Sw4 via the negative-side bus 32. The W-phase input terminal of the rotating electrical machine 10 is connected to the connection point between the W-phase second switch Sw2 and the W-phase third switch Sw3. In addition, the cathode of the fifth clamping diode Dc5 is connected to the connection point between the W-phase first switch Sw1 and the W-phase second switch Sw2, and the cathode of the sixth clamping diode Dc6 is connected to the anode of the fifth clamping diode Dc5. The connection point between the W-phase third switch Sw3 and the W-phase fourth switch Sw4 is connected to the anode of the sixth clamping diode Dc6. In addition, the freewheeling diodes Dw1 , Dw2 , Dw3 , and Dw4 are connected in antiparallel to the switches Sw1 , Sw2 , Sw3 , and Sw4 of the W phase.

[0058] A neutral point O is connected to a connection point between the first clamp diode Dc1 and the second clamp diode Dc2 , a connection point between the third clamp diode Dc3 and the fourth clamp diode Dc4 , and a connection point between the fifth clamp diode Dc5 and the sixth clamp diode Dc6 .

[0059] The control device 40 performs a boost control in a state where the inverter 30 and the low-voltage charger 51 are connected via the negative-side connection portion 61 and the neutral point connection portion 62. The boost control is described in detail below. As a boost control, the control device 40 turns on the first switch and the second switch in a specific phase that is a part of each phase, and the third switch and the fourth switch in the specific phase alternately. In addition, the control device 40 turns off the first switch, the third switch, and the fourth switch in the phase other than the specific phase in each phase, and turns on the second switch in the phase other than the specific phase. Figure 7 and Figure 8 The current path in the boost control is shown when the specific phase is phase W. Alternatively, the control device 40 may open either the third switch or the fourth switch in phases other than the specific phase instead of opening both the third switch and the fourth switch in phases other than the specific phase.

[0060] When the specific phase is the W phase, in the implementation of the boost control, the U-phase first switch Su1, the V-phase first switch Sv1, the U-phase third switch Su3, the V-phase third switch Sv3, the U-phase fourth switch Su4, and the V-phase fourth switch Sv4 are turned off, and the U-phase second switch Su2 and the V-phase second switch Sv2 are turned on. In addition, the W-phase first switch Sw1 and the W-phase second switch Sw2, and the W-phase third switch Sw3 and the W-phase fourth switch Sw4 are alternately turned on.

[0061] Figure 7The current path when the W-phase first switch Sw1 and the W-phase second switch Sw2 are turned off and the W-phase third switch Sw3 and the W-phase fourth switch Sw4 are turned on is shown. In this case, a closed loop is formed including the low-voltage charger 51, the neutral point connection part 62, the neutral point switch T3, the first clamping diode Dc1 and the third clamping diode Dc3, the U-phase second switch Su2 and the V-phase second switch Sv2, the windings 13U, 13V, 13W, the W-phase third switch Sw3 and the W-phase fourth switch Sw4, the negative-side bus 32, the negative-side switch T2 and the negative-side connection part 61. As a result, magnetic energy is accumulated in the windings 13U, 13V, 13W.

[0062] Figure 8 The figure shows the current path when the W-phase first switch Sw1 and the W-phase second switch Sw2 are turned on, and the W-phase third switch Sw3 and the W-phase fourth switch Sw4 are turned off. In this case, a closed loop is formed including the low-voltage charger 51, the neutral point connection part 62, the neutral point switch T3, the first clamping diode Dc1 and the third clamping diode Dc3, the U-phase second switch Su2, the V-phase second switch Sv2, the windings 13U, 13V, 13W, the W-phase first switch Sw1 and the W-phase second switch Sw2, the positive-side bus 31, the battery 20, the negative-side switch T2, and the negative-side connection part 61. As a result, the charging voltage of the low-voltage charger 51 is boosted, and the boosted voltage is supplied to the battery 20.

[0063] In addition, the specific phase may be a phase other than the W phase. When the specific phase is the U phase, the V phase first switch Sv1, the W phase first switch Sw1, the V phase third switch Sv3, the W phase third switch Sw3, the V phase fourth switch Sv4, and the W phase fourth switch Sw4 are turned off, and the V phase second switch Sv2 and the W phase second switch Sw2 are turned on. In addition, the U phase first switch Su1 and the U phase second switch Su2, and the U phase third switch Su3 and the U phase fourth switch Su4 are turned on alternately. When the specific phase is the V phase, the U phase first switch Su1, the W phase first switch Sw1, the U phase third switch Su3, the W phase third switch Sw3, the U phase fourth switch Su4, and the W phase fourth switch Sw4 are turned off, and the U phase second switch Su2 and the W phase second switch Sw2 are turned on. In addition, the V phase first switch Sv1 and the V phase second switch Sv2, and the V phase third switch Sv3 and the V phase fourth switch Sv4 are turned on alternately.

[0064] When the specific phase is the U phase or the V phase, the W phase first switch Sw1, the W phase third switch Sw3, and the W phase fourth switch Sw4 are turned off, and the W phase second switch Sw2 is turned on. In addition, the U phase first switch Su1, the V phase first switch Sv1, the U phase second switch Su2, the V phase second switch Sv2, and the U phase third switch Su3, the V phase third switch Sv3, the U phase fourth switch Su4, and the V phase fourth switch Sv4 are turned on alternately. When the specific phase is the V phase or the W phase, the U phase first switch Su1, the U phase third switch Su3, and the U phase fourth switch Su4 are turned off, and the U phase second switch Su2 is turned on. In addition, the V phase first switch Sv1, the W phase first switch Sw1, the V phase second switch Sv2, the W phase second switch Sw2, and the V phase third switch Sv3, the W phase third switch Sw3, the V phase fourth switch Sv4, and the W phase fourth switch Sw4 are turned on alternately. When the specific phase is the U phase or the W phase, the V phase first switch Sv1, the V phase third switch Sv3, and the V phase fourth switch Sv4 are turned off, and the V phase second switch Sv2 is turned on. In addition, the U phase first switch Su1, the W phase first switch Sw1, the U phase second switch Su2, the W phase second switch Sw2, the U phase third switch Su3, the W phase third switch Sw3, the U phase fourth switch Su4, and the W phase fourth switch Sw4 are turned on alternately.

[0065] In addition, similarly to the first embodiment, the control device 40 may control the current to flow through the inverter 30a and the respective phase windings 13U, 13V, and 13W so that the q-axis current becomes zero.

[0066] <Other embodiments> For example, the above-mentioned embodiment may be modified as follows.

[0067] The neutral point wiring 35 may be connected to an electric load instead of being connected to the neutral point connection portion 62. The electric load may be driven by the power supplied from the battery 20. Examples of the electric load are a dynamic compressor and a DCDC converter. The electric compressor is provided for air conditioning in the vehicle interior and is driven to circulate the refrigerant of the refrigeration cycle. The DCDC converter is driven to step down the input voltage and supply it to the electric compressor. In the present embodiment, the electric load corresponds to an "electrical device".

[0068] Here, it is considered that there is a situation where the electric load is driven while the rotating electric machine 10 is driven. In this situation, there is a possibility that a voltage higher than the withstand voltage of the electric load is applied to the electric load. In order to cope with this situation, it is considered to add a dedicated circuit to reduce the voltage applied to the electric load, but in this case, the power conversion device may be enlarged. In addition, although it is considered to increase the withstand voltage of the electric load, in this case, the manufacturing cost of the motor control system may increase.

[0069] In view of this, in the present embodiment, the electric load and the neutral point O are connected via the neutral point wiring 35. In this case, the electric load is connected to the second end of the second capacitor 22 via the negative electrode side wiring 34, so that the electric load is connected in parallel with the second capacitor 22. In the state where the electric load and the second capacitor 22 are connected in parallel, the control device 40 turns on and off the switches SUH to SWL and QU to QW in order to drive the rotating electric machine 10.

[0070] According to the present embodiment, in a state where the electric load is connected in parallel with the second capacitor 22, the switches SUH to SWL, QU to QW are turned on and off. In this case, the output voltage of the second capacitor 22 is applied to the electric load. Therefore, the voltage applied to the electric load is lower than that in a case where the electric load is connected in parallel with the battery 20. As a result, it is possible to suppress the addition of a dedicated circuit for stepping down the voltage supplied to the electric load, and it is possible to suppress the increase in the withstand voltage of the electric load.

[0071] Alternatively, instead of connecting the electric load and the second end of the second capacitor 22 via the negative electrode wiring 34, the electric load and the first end of the first capacitor 21 may be connected via the positive electrode wiring 33. In this case, the electric load is connected in parallel with the first capacitor 21.

[0072] The positive electrode side wiring 33 , the positive electrode side connection portion 60 and the positive electrode side switch T1 may not be provided. In other words, the motor control system may not handle charging by the high-voltage charger 50 .

[0073] When the control device 40 controls the current to flow through the inverter 30 and each phase winding 13U, 13V, 13W as the boost control, it is also possible to control the q-axis current to be close to 0 instead of setting the q-axis current to 0. For example, the control device 40 may set the q-axis command current Iq* to a value that can maintain the rotation stop state of the rotor 11 of the rotary electric machine 10 during the implementation of the boost control. In addition, for example, the control device 40 may also perform a reduction process of setting the q-axis command current Iq* to a value close to 0 and reducing the torque transmitted by the power transmission mechanism 14 to the drive wheel 12. The reduction process is, for example, at least one of a process of reducing the degree of transmission of the torque transmitted from the rotating shaft to the axle through the clutch and a process of reducing the gear ratio of the transmission. Thus, even when the q-axis current is close to 0 during the boost control, the rotation of the rotor 11 of the rotary electric machine 10 can be suppressed.

[0074] As the clamp switches of each phase, instead of connecting their sources, their drains may be connected. In this case, for example, the source of one of the switches constituting the U-phase clamp switch QU is connected to the connection point of the U-phase upper arm switch SUH and the U-phase lower arm switch SUL, and the source of the other switch is connected to the neutral point O.

[0075] · As the clamping switch for each phase, it is not limited to the structure of connecting a set of switches in series. Fig. 9 As shown, a reverse blocking IGBT (RB-IGBT) may also be used as each phase clamp switch QUa, QVa, QWa. The connection point of the U-phase upper arm switch SUH and the U-phase lower arm switch SUL can be connected to the neutral point O via the U-phase clamp switch QUa connected in reverse parallel to each other. The connection point of the V-phase upper arm switch SVH and the V-phase lower arm switch SVL can be connected to the neutral point O via the V-phase clamp switch QVa connected in reverse parallel to each other. The connection point of the W-phase upper arm switch SWH and the W-phase lower arm switch SWL can be connected to the neutral point O via the W clamp switch QWa connected in reverse parallel to each other.

[0076] In the first embodiment, the semiconductor switch constituting the inverter is not limited to an N-channel MOSFET, and may be, for example, an IGBT. In the second embodiment, the semiconductor switch constituting the inverter is not limited to an IGBT, and may be an N-channel MOSFET.

[0077] The rotating electric machine is not limited to a rotating electric machine in which the windings of each phase are connected in star connection, but may be a rotating electric machine connected in delta connection. In addition, the rotating electric machine and the inverter are not limited to three-phase ones, but may be two-phase ones or four-phase ones or more.

[0078] The object on which the power conversion device is installed is not limited to a vehicle, and may be a mobile object such as an airplane or a ship. When the mobile object is an airplane, the rotating electric machine 10 is a flight power source for the airplane, and when the mobile object is a ship, the rotating electric machine 10 is a navigation power source for the ship. In addition, the object on which the power conversion device is installed is not limited to a mobile object.

[0079] · Hereinafter, characteristic structures extracted from the above-mentioned embodiments will be described. [Structure 1] A power conversion device, the power conversion device is applicable to a system, the system comprising: a storage battery (20); and An electrical device (51), the electrical device being electrically connectable to the battery, the power conversion device comprising: A three-level inverter (30), the three-level inverter being electrically connected to the battery; and A rotating electric machine (10), the rotating electric machine having windings (13U, 13V, 13W) electrically connected to the three-level inverter, The above three-level inverter has: a first power storage unit (21) and a second power storage unit (22) connected in series; and switches (SUH to SWL, QU to QW, Su1 to Sw4), the switches connecting the winding to any one of the positive side of the first power storage unit, the negative side of the first power storage unit and the neutral point between the positive side of the second power storage unit, and the negative side of the second power storage unit, The positive electrode side of the first power storage unit is connected to the positive electrode terminal of the battery. The negative electrode side of the second power storage unit is connected to the negative electrode terminal of the battery. The above-mentioned power conversion device comprises: a connecting portion (35, 62) that connects the electrical device to the three-level inverter and is electrically connectable to the battery via the neutral point; and A control unit (40) performs switch control of each of the switches to transmit power between the electrical device and the battery when the three-level inverter and the electrical device are connected via the connection unit. [Structure 2] According to the power conversion device described in structure 1, The electrical device is arranged outside the power conversion device and is a charger (51) for charging the storage battery. The connection parts are a neutral point connection part (62) and a negative electrode side connection part (61), The neutral point connecting unit connects the positive terminal of the charger to the neutral point. The negative electrode side connecting portion connects the negative electrode side terminal of the charger to the negative electrode side of the second power storage unit. The control unit performs boost control as the switch control when the charger and the three-level inverter are connected via the neutral point connection unit and the negative electrode side connection unit. The boost control boosts the charging voltage of the charger by passing current through the three-level inverter and the winding, and supplies the boosted voltage to the battery. [Structure 3] According to the power conversion device described in Structure 2, The rotating electrical machine is a multi-phase rotating electrical machine. As the switches, the three-level inverter has the following components corresponding to the number of phases: an upper arm switch and a lower arm switch connected in series; and a clamp switch (QU to QW) for switching on and off the current flowing between the winding and the neutral point, As the above-mentioned boost control, the above-mentioned control unit disconnects the above-mentioned clamping switch in a specific phase which is a part of each phase, and alternately connects the upper arm switch and the lower arm switch in the above-mentioned specific phase, disconnects the above-mentioned upper arm switch and the lower arm switch in the phase other than the above-mentioned specific phase in each phase, and connects the above-mentioned clamping switch in the phase other than the above-mentioned specific phase. [Structure 4] According to the power conversion device described in Structure 2, The rotating electrical machine is a multi-phase rotating electrical machine. As the switches, the three-level inverter includes first switches (Su1 to Sw1), second switches (Su2 to Sw2), third switches (Su3 to Sw3), and fourth switches (Su4 to Sw4) connected in series in accordance with the number of phases. The three-level inverter has first clamping diodes (Dc1, Dc3, Dc5) and second clamping diodes (Dc2, Dc4, Dc6) corresponding to the number of phases. The high potential side terminal of the first switch is connected to the positive terminal of the battery. The low potential side terminal of the fourth switch is connected to the negative terminal of the battery. A connection point between the second switch and the third switch is connected to the winding. The cathode of the first clamping diode is connected to the connection point between the first switch and the second switch. The cathode of the second clamping diode is connected to the anode of the first clamping diode. The anode of the second clamping diode is connected to a connection point of the third switch and the fourth switch. The neutral point is connected to the connection point between the first clamping diode and the second clamping diode. As the voltage step-up control, the control unit turns on the first switch and the second switch, and the third switch and the fourth switch alternately in a specific phase that is a part of each phase. In phases other than the specific phase among the phases, control is performed such that the first switch is turned off, the second switch is turned on, and at least one of the third switch and the fourth switch is turned off. [Structure 5] According to the power conversion device described in any one of Configurations 2 to 4, the control unit performs control to make a current flow through the three-level inverter and the winding so that the q-axis current becomes zero or close to zero as the boost control. [Structure 6] According to the power conversion device described in structure 5, The above system is an on-board system installed in a vehicle. The rotor (11) of the rotating electrical machine can transmit power to the driving wheels (12) of the vehicle. [Structure 7] The power conversion device according to any one of Structures 2 to 6, wherein: The charger is a low-voltage charger (51) having a charging voltage lower than the rated voltage of the battery. The connecting part includes: The above-mentioned neutral point connection part; The negative electrode side connecting portion; and A positive electrode side connection unit (60) capable of connecting a positive electrode side terminal of a high voltage charger (50) having a higher charging voltage than the low voltage charger to the positive electrode side of the first power storage unit.

[0080] Although the present disclosure is described based on the embodiments, it should be understood that the present disclosure is not limited to the above-mentioned embodiments and structures. The present disclosure also includes various modifications and modifications within the equivalent range. In addition, various combinations and methods, and other combinations and methods containing only one element, above or below them, also belong to the scope and thought range of the present disclosure.

Claims

1. A power conversion device, the power conversion device being applicable to a system, the system comprising: Storage battery (20); and an electrical device (51) which can be electrically connected to the battery, The power conversion device comprises: a three-level inverter (30), the three-level inverter being electrically connected to the storage battery; and A rotating electric machine (10) having windings (13U, 13V, 13W) electrically connected to the three-level inverter, The three-level inverter has: a first power storage unit (21) and a second power storage unit (22) connected in series; and switches (SUH to SWL, QU to QW, Su1 to Sw4) that connect the winding to any one of the positive side of the first power storage unit, the neutral point between the negative side of the first power storage unit and the positive side of the second power storage unit, and the negative side of the second power storage unit, The positive electrode side of the first power storage unit is connected to the positive electrode terminal of the battery. The negative electrode side of the second power storage unit is connected to the negative electrode terminal of the battery. The power conversion device comprises: a connection portion (35, 62) that connects the electrical device to the three-level inverter and is electrically connectable to the battery via the neutral point; and A control unit (40) performs switching control of each of the switches to transmit power between the electrical device and the battery in a state where the three-level inverter and the electrical device are connected via the connection unit.

2. The power conversion device according to claim 1, characterized in that: The electrical device is arranged outside the power conversion device and is a charger (51) for charging the storage battery. The connecting parts are a neutral point connecting part (62) and a negative electrode side connecting part (61), The neutral point connecting unit connects the positive terminal of the charger to the neutral point. The negative electrode side connecting portion connects the negative electrode side terminal of the charger to the negative electrode side of the second power storage portion. The control unit performs a boost control as the switch control when the charger and the three-level inverter are connected via the neutral point connection unit and the negative side connection unit. The boost control boosts the charging voltage of the charger by passing a current through the three-level inverter and the winding, and supplies the boosted voltage to the battery.

3. The power conversion device according to claim 2, characterized in that: The rotating electrical machine is a multi-phase rotating electrical machine, As the switches, the three-level inverter has, corresponding to the number of phases: An upper arm switch and a lower arm switch (SUH to SWL) connected in series; and a clamp switch (QU-QW) for switching on and off the current flowing between the winding and the neutral point, As the boost control, the control unit disconnects the clamp switch in a specific phase which is a part of each phase, and alternately connects the upper arm switch and the lower arm switch in the specific phase, disconnects the upper arm switch and the lower arm switch in a phase other than the specific phase in each phase, and connects the clamp switch in the phase other than the specific phase.

4. The power conversion device according to claim 2, characterized in that: The rotating electrical machine is a multi-phase rotating electrical machine, As the switches, the three-level inverter includes a first switch (Su1 to Sw1), a second switch (Su2 to Sw2), a third switch (Su3 to Sw3), and a fourth switch (Su4 to Sw4) connected in series corresponding to the number of phases. The three-level inverter has first clamping diodes (Dc1, Dc3, Dc5) and second clamping diodes (Dc2, Dc4, Dc6) corresponding to the number of phases. The high potential side terminal of the first switch is connected to the positive terminal of the battery, The low potential side terminal of the fourth switch is connected to the negative terminal of the battery, The connection point of the second switch and the third switch is connected to the winding, A cathode of the first clamping diode is connected to a connection point between the first switch and the second switch. The cathode of the second clamping diode is connected to the anode of the first clamping diode. A connection point between the third switch and the fourth switch is connected to the anode of the second clamping diode. The neutral point is connected to a connection point between the first clamping diode and the second clamping diode. As the boost control, the control unit alternately turns on the first switch and the second switch, and the third switch and the fourth switch in a specific phase which is a part of each phase, and controls the first switch to be turned off, the second switch to be turned on, and at least one of the third switch and the fourth switch to be turned off in a phase other than the specific phase.

5. The power conversion device according to any one of claims 2 to 4, characterized in that: The control unit performs control for causing a current to flow through the three-level inverter and the winding so that a q-axis current becomes zero or close to zero as the voltage boost control.

6. The power conversion device according to claim 5, characterized in that: The system is an on-board system installed in a vehicle. The rotor (11) of the rotating electric machine can transmit power to the driving wheels (12) of the vehicle.

7. The power conversion device according to claim 2, characterized in that: The charger is a low-voltage charger (51) having a charging voltage lower than the rated voltage of the battery. The connecting portion comprises: The neutral point connection portion; the negative electrode side connecting portion; and A positive electrode side connection unit (60) capable of connecting a positive electrode side terminal of a high voltage charger (50) having a higher charging voltage than the low voltage charger to the positive electrode side of the first power storage unit.

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