POWER CONVERSION DEVICE, PROGRAM, AND METHOD FOR CONTROLLING POWER CONVERSION DEVICE

Abstract

To provide a power conversion device capable of reducing a noise generated at temperature rising control of a battery pack.SOLUTION: A power conversion device 10 comprises: a rotary electric machine 40 that has respective phase coils 41U, 41V, and 41W; an inverter 30 that has series connection bodies of upper and lower arm switches QUH, QVH, QWH, QUL, QVL, and QWL; and a capacitor 31 connected in parallel with the series connection bodies. Further, the power conversion device 10 comprises: a connection path 60 electrically connecting between an intermediate terminal B of a battery pack 20 and a neutral point O; and a control device 70 that performs switching control of the inverter 30 so as to apply a current between a first accumulator battery 21 and a second accumulator battery 22 configuring the battery pack 20 via the inverter 30, the phase coils 41U, 41V, and 41W and the connection path 60.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention , electric Force conversion device , program, and method for controlling power conversion device - Patents.com Regarding. [Background technology]

[0002] As an example of this type of power conversion device, one that controls the temperature rise of a storage battery by exchanging reactive power between the storage battery and a capacitor via an inverter is known, as shown in Patent Document 1. In more detail, when a current flows from the storage battery to the capacitor, the inverter and windings are used as a boost chopper circuit, and when a current flows from the capacitor to the storage battery, the inverter and windings are used as a boost chopper circuit. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5865736 Summary of the Invention [Problem to be solved by the invention]

[0004] In the power conversion device described in Patent Document 1, reactive power is exchanged between the storage battery and the capacitor, so the terminal voltage of the capacitor fluctuates in proportion to the reactive power. This fluctuation may cause the terminal voltage of the capacitor to exceed the allowable upper limit determined by the voltage resistance performance of the capacitor, which may reduce the reliability of the capacitor.

[0005] On the other hand, the terminal voltage of the capacitor may become excessively low due to fluctuations in the terminal voltage of the capacitor. When a current flows from the storage battery to the capacitor via the inverter, the terminal voltage of the capacitor needs to be higher than the terminal voltage of the storage battery. Therefore, if the terminal voltage of the capacitor becomes excessively low, there is a concern that the current flowing from the storage battery to the capacitor cannot be controlled to the desired command current.

[0006] To address the above-described problems, it is necessary to reduce the amount of fluctuation in the terminal voltage of the capacitor. One possible solution to this problem is to increase the capacitance of the capacitor. However, this would result in an increase in the size of the capacitor.

[0007] On the other hand, in order to reduce the amount of fluctuation, other than increasing the capacitance of the capacitor, it is also possible to consider increasing the frequency of the reactive power (ripple current), but this will increase noise and deteriorate the NVH characteristics of the power conversion device.

[0008] A primary object of the present invention is to provide a power conversion device, a program, and a control method for a power conversion device that can reduce noise generated during temperature increase control of a storage battery. [Means for solving the problem]

[0009] The first configuration is: A power conversion device (10) electrically connectable to polyphase windings (41U, 41V, 41W, 41X, 41Y) of a rotating electric machine (40), a first storage battery (21), and a second storage battery (22), and electrically connects between a negative electrode side of the first storage battery and a positive electrode side of the second storage battery and a neutral point (O) of the windings of each phase by a connection path (60), an inverter (30) having a series connection of upper arm switches (QUH, QVH, QWH, QXH, QYH) and lower arm switches (QUL, QVL, QWL, QXL, QYL) corresponding to the number of phases; and a control unit (70) that performs control processing to synchronize the switching control of the upper arm switches of all phases and synchronize the switching control of the lower arm switches of all phases so that current flows between the first storage battery and the second storage battery via the inverter, the windings, and the connection path.

[0010] According to the first configuration, switching control of the upper arm switch and the lower arm switch is performed so that a current flows between the first storage battery and the second storage battery via the inverter, the winding, and the connection path. As a result, a ripple current flows between the first storage battery and the second storage battery, and the first storage battery and the second storage battery are heated. Then, in the switching control, the switching control of the upper arm switches of all phases is synchronized, and the switching control of the lower arm switches of all phases is synchronized. In this case, the windings of each phase are regarded as an equivalent circuit in which the windings are connected in parallel, and the inductance of the current path during the switching control can be reduced. This makes it possible to increase the amount of change in the current flowing to the neutral point in one switching period of the switching control. As a result, it is possible to provide a power conversion device with a new configuration that can use a large current for temperature raising control of the first storage battery and the second storage battery.

[0011] No. In the first configuration, the upper arm switch Chi A capacitor is connected in parallel to the series connection of the lower arm switches. The capacity of the storage battery is sufficiently larger than that of the capacitor. Therefore, the increase and decrease in the terminal voltage with respect to the charge and discharge current of the storage battery is sufficiently smaller than the increase and decrease in the terminal voltage with respect to the charge and discharge current of the capacitor. Therefore, by exchanging power between the storage batteries, rather than between the capacitor and the storage battery, the amount of fluctuation in the terminal voltage of the capacitor during temperature rise control can be reduced without increasing the switching frequency of the upper and lower arm switches. This makes it possible to reduce the amount of fluctuation in the terminal voltage of the capacitor without increasing the switching frequency of the upper and lower arm switches. Therefore, according to the second configuration described above, it is possible to reduce noise generated during temperature rise control of the first and second storage batteries. [Brief description of the drawings]

[0012] [Figure 1] 1 is a configuration diagram of a power conversion device according to a first embodiment. [Diagram 2] 4 is a flowchart showing a processing procedure of the control device. [Diagram 3] FIG. [Figure 4] FIG. [Diagram 5] FIG. 4 is a diagram showing a method for setting a command current. [Figure 6] 4 is a time chart showing the transition of the control mode of the switch, etc.; [Figure 7] FIG. [Figure 8] FIG. 13 is a diagram showing a simulation result according to a comparative example. [Figure 9] 6 is a time chart showing the transition of the control mode of the switch according to the first modification of the first embodiment. [Figure 10]6 is a time chart showing the transition of the control mode of the switch according to the first modification of the first embodiment. [Figure 11] FIG. 4 is a functional block diagram of a control device according to a second modified example of the first embodiment. [Figure 12] 4 is a time chart showing a hysteresis control mode. [Figure 13] FIG. 11 is a diagram showing a method of correcting a command current according to the second embodiment. [Figure 14] FIG. 4 is a diagram showing a method of correcting a command current. [Figure 15] 11 is a flowchart showing a processing procedure of a control device according to a third embodiment. [Figure 16] FIG. 13 is a configuration diagram of a power conversion device according to a fourth embodiment. [Figure 17] FIG. 13 is a configuration diagram of a power conversion device according to a fifth embodiment. [Figure 18] FIG. [Figure 19] 4 is a time chart showing the transition of the control mode of the switch, etc.; [Figure 20] FIG. [Figure 21] FIG. 13 is a functional block diagram of a control device according to a first modified example of the fifth embodiment. [Figure 22] 13 is a time chart showing the transition of the control mode of the switch according to the second modification of the fifth embodiment. [Diagram 23] FIG. 13 is a configuration diagram of a power conversion device according to a sixth embodiment. [Figure 24] FIG. 13 is a configuration diagram of a power conversion device according to a seventh embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] First Embodiment DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of a power converter according to the present invention will now be described with reference to the drawings. In this embodiment, the power converter is mounted on a vehicle.

[0014] 1, the power conversion device 10 includes an inverter 30 and a rotating electric machine 40. The power conversion device 10 has a function of exchanging power between the battery pack 20 and the rotating electric machine 40 via the inverter 30 in order to raise the temperature of the battery pack 20.

[0015] The rotating electric machine 40 is a three-phase synchronous machine, and includes star-connected U-, V-, and W-phase windings 41U, 41V, and 41W as stator windings. The phase windings 41U, 41V, and 41W are arranged with an electrical angle of 120° between each other. The rotating electric machine 40 is, for example, a permanent magnet synchronous machine. In this embodiment, the rotating electric machine 40 is an in-vehicle main engine, and serves as a power source for running the vehicle.

[0016] The inverter 30 includes three phases of series-connected upper arm switches QUH, QVH, and QWH and lower arm switches QUL, QVL, and QWL. In this embodiment, a voltage-controlled semiconductor switching element, specifically an IGBT, is used as each switch QUH, QVH, QWH, QUL, QVL, and QWL. Therefore, the high-potential terminal of each switch QUH, QVH, QWH, QUL, QVL, and QWL is a collector, and the low-potential terminal is an emitter. Diodes DUH, DVH, DWH, DUL, DVL, and DWL are connected in inverse parallel to each switch QUH, QVH, QWH, QUL, QVL, and QWL as freewheel diodes.

[0017] A first end of the U-phase winding 41U is connected to the emitter of the U-phase upper arm switch QUH and the collector of the U-phase lower arm switch QUL via a U-phase conductive member 32U such as a bus bar. A first end of the V-phase winding 41V is connected to the emitter of the V-phase upper arm switch QVH and the collector of the V-phase lower arm switch QVL via a V-phase conductive member 32V such as a bus bar. A first end of the W-phase winding 41W is connected to the emitter of the W-phase upper arm switch QWH and the collector of the W-phase lower arm switch QWL via a W-phase conductive member 32W such as a bus bar. Second ends of the U-, V-, and W-phase windings 41U, 41V, and 41W are connected to each other at a neutral point O. In this embodiment, the number of turns of each phase winding 41U, 41V, and 41W is set to be the same. As a result, for example, the inductance of each phase winding 41U, 41V, and 41W is set to be the same.

[0018] The collectors of the upper arm switches QUH, QVH, and QWH are connected to the positive terminal of the battery pack 20 by a positive bus Lp such as a bus bar. The emitters of the lower arm switches QUL, QVL, and QWL are connected to the negative terminal of the battery pack 20 by a negative bus Ln such as a bus bar.

[0019] The power conversion device 10 includes a capacitor 31 that connects the positive bus Lp and the negative bus Ln. The capacitor 31 may be built in the inverter 30 or may be provided outside the inverter 30.

[0020] The battery pack 20 is configured as a series connection of battery cells acting as single batteries, and has a terminal voltage of, for example, several hundred volts. In this embodiment, the terminal voltages (for example, rated voltages) of the battery cells constituting the battery pack 20 are set to be the same. For example, secondary batteries such as lithium ion batteries can be used as the battery cells.

[0021] In this embodiment, among the battery cells constituting the battery pack 20, a series connection of multiple battery cells on the high potential side constitutes the first storage battery 21, and a series connection of multiple battery cells on the low potential side constitutes the second storage battery 22. That is, the battery pack 20 is divided into two blocks. In this embodiment, the number of battery cells constituting the first storage battery 21 is the same as the number of battery cells constituting the second storage battery 22. Therefore, the terminal voltage (e.g., rated voltage) of the first storage battery 21 is the same as the terminal voltage (e.g., rated voltage) of the second storage battery 22.

[0022] In the battery pack 20, an intermediate terminal B is connected to the negative terminal of the first storage battery 21 and the positive terminal of the second storage battery 22.

[0023] The power conversion device 10 includes a monitoring unit 50 (corresponding to a voltage information detection unit). The monitoring unit 50 monitors the terminal voltage, SOC, SOH, temperature, and the like of each battery cell that constitutes the battery pack 20.

[0024] The power conversion device 10 includes a connection path 60 and a connection switch 61. The connection path 60 electrically connects the intermediate terminal B and the neutral point O of the battery pack 20. The connection switch 61 is provided on the connection path 60. In this embodiment, a relay is used as the connection switch 61. When the connection switch 61 is turned on, the intermediate terminal B and the neutral point O are electrically connected. On the other hand, when the connection switch 61 is turned off, the intermediate terminal B and the neutral point O are electrically disconnected.

[0025] The power conversion device 10 includes a current sensor 62 that detects a current flowing through the connection path 60. A detection value of the current sensor 62 is input to a control device 70 (corresponding to a control unit) included in the power conversion device 10.

[0026] The control device 70 is mainly configured with a microcomputer, and performs switching control of each switch constituting the inverter 30 so as to feedback control the control amount of the rotary electric machine 40 to its command value. The control amount is, for example, torque.

[0027] The control device 70 controls the on / off of the connection switch 61, and is capable of communicating with the monitoring unit 50. The control device 70 is also capable of communicating with a higher-level control device 80 provided outside the power conversion device 10. The higher-level control device 80 supervises the control of the vehicle.

[0028] The control device 70 executes programs stored in a storage device provided therein to realize various control functions. The various functions may be realized by electronic circuits, which are hardware, or may be realized by both hardware and software.

[0029] Next, a description will be given of the temperature rise control of the battery pack 20 executed by the control device 70. Fig. 2 is a flowchart showing the procedure of the temperature rise control process. This process is repeatedly executed by the control device 70 at a predetermined control period, for example.

[0030] In step S10, it is determined whether or not there is a request to increase the temperature of the battery pack 20. For example, if it is determined that there is an instruction to increase the temperature of the battery pack 20 from the upper control device 80, or if it is determined that the temperature of the battery pack 20 detected by the monitoring unit 50 is lower than the threshold temperature, it may be determined that there is a request to increase the temperature. Here, the temperature compared with the threshold temperature may be, for example, the lowest temperature among the detected temperatures of each battery cell, or the average temperature of each battery cell calculated based on the detected temperatures of each battery cell.

[0031] In this embodiment, a situation in which a positive determination is made in step S10 is assumed to be a situation in which the vehicle is stopped before the rotating electric machine 40 is driven.

[0032] If it is determined in step S10 that there is no temperature increase request, the process proceeds to step S11, where it is determined whether there is a request to drive the rotating electric machine 40. In this embodiment, the drive request includes a request to run the vehicle by driving the rotating electric machine 40 to rotate.

[0033] If it is determined in step S11 that there is no drive request, the process proceeds to step S12, where the standby mode is set. By setting this mode, the switches QUH to QWL of the inverter 30 are controlled to be turned off. Then, in step S13, the connection switch 61 is controlled to be turned off. This electrically disconnects the intermediate terminal B and the neutral point O.

[0034] If it is determined in step S11 that there is a drive request, the process proceeds to step S14, where the rotating electric machine 40 is set to a drive mode. 5 In this case, the connection switch 61 is turned on. centre This controls the intermediate terminal B and the neutral point O. The electricity In terms of Blocking Thereafter, in step S16, switching control is performed on each of the switches QUH-QWL of the inverter 30 to rotate the rotating electric machine 40. This rotates the drive wheels of the vehicle, allowing the vehicle to run. The switching control in step S16 may be performed using, for example, PWM based on a magnitude comparison between the command voltage applied to each of the phase windings 41U-41W and a carrier signal (for example, a triangular wave signal), or a pulse pattern.

[0035] If it is determined in step S10 that there is a temperature increase request, the process proceeds to step S17, where the temperature increase control mode is set, and in step S18, the connection switch 61 is controlled to be turned on.

[0036] In step S19, a temperature-raising PWM control is performed to raise the temperature of the battery pack 20. This control will be described below.

[0037] Fig. 3(a) shows an equivalent circuit of the power conversion device 10 used in the temperature-rise PWM control. In Fig. 3(a), each phase winding 41U-41W is shown as a winding 41, each upper arm switch QUH, QVH, QWH is shown as an upper arm switch QH, and each upper arm diode DUH, DVH, DWH is shown as an upper arm diode DH. In addition, each lower arm switch QUL, QVL, QWL is shown as a lower arm switch QL, and each lower arm diode DUL, DVL, DWL is shown as a lower arm diode DL.

[0038] The equivalent circuit of Fig. 3(a) can be shown as the equivalent circuit of Fig. 3(b). The circuit of Fig. 3(b) is a step-up / step-down chopper circuit capable of bidirectional power transmission between the first storage battery 21 and the second storage battery 22. In Fig. 3(b), VBH indicates the terminal voltage of the first storage battery 21, IBH indicates the current flowing to the first storage battery 21, VBL indicates the terminal voltage of the second storage battery 22, and IBL indicates the current flowing to the second storage battery 22. When a charging current flows through the first and second storage batteries 21 and 22, IBH and IBL are negative, and when a discharging current flows through the first and second storage batteries 21 and 22, IBH and IBL are positive. In addition, VR indicates the terminal voltage of the winding 41, and IR indicates the current flowing to the neutral point O. When a current flows from the winding 41 to the intermediate terminal B in a positive direction to the neutral point O, IR is negative, and when a current flows in the opposite direction to the neutral point O, IR is positive.

[0039] 3(b), when the upper arm switch QH is turned on, the terminal voltage VR of the winding 41 becomes "VBH." On the other hand, when the lower arm switch QL is turned on, the terminal voltage VR of the winding 41 becomes "-VBL." In other words, when the upper arm switch QH is turned on, an excitation current can be caused to flow in the positive direction through the winding 41, and when the lower arm switch QL is turned on, an excitation current can be caused to flow in the negative direction through the winding 41.

[0040] FIG. 4 shows a block diagram of the temperature rise PWM control.

[0041] In the control device 70, the current deviation calculation unit 71 calculates the current deviation by subtracting the current detected by the current sensor 62 (hereinafter, the detected current IMr) from the command current IM*. In this embodiment, the command current IM* is set as a sine wave as shown in FIG. 5. More specifically, the command current IM* is set so that the positive command current IM* and the negative command current IM* are point-symmetric with respect to the zero cross timing of the command current IM* in one cycle Tc of the command current IM*. As a result, the period from the zero up-cross timing to the zero down-cross timing of the command current IM* becomes the same as the period from the zero down-cross timing to the zero up-cross timing of the command current IM*. Also, in one cycle Tc of the command current IM*, the area S1 of the first region and the area S2 of the second region become equal. The first region S1 is a region surrounded by the time axis from the zero up-cross timing to the zero down-cross timing of the command current IM* and the positive command current IM* in one cycle Tc of the command current IM*. The second region is a region surrounded by the time axis from the zero down-cross timing to the zero up-cross timing of the command current IM* in one cycle Tc and the negative command current IM*. By setting "S1 = S2", the balance of the charge / discharge current of the first storage battery 21 and the second storage battery 22 in one cycle Tc can be matched, and the difference between the terminal voltage of the first storage battery 21 and the terminal voltage of the second storage battery 22 can be suppressed from increasing due to the temperature rise control.

[0042] The frequency fc of the command current IM*, which is the reciprocal of one period Tc of the command current IM*, is desirably set to, for example, a frequency on the lower limit side of the human audible range. Specifically, the frequency fc is desirably set to 1 kHz or less, which is a frequency range in which the correction value (dB) is 0 or less in the A-characteristic, and more desirably set to a frequency between 30 Hz and 100 Hz (for example, 50 Hz).

[0043] The feedback control unit 72 calculates a duty ratio Duty as an operation amount for feedback controlling the calculated current deviation to 0. The duty ratio Duty is a value that determines the ratio (Ton / Tsw) of the on-time Ton in one switching period Tsw of each of the switches QUH to QWL. The feedback control used by the feedback control unit 72 may be, for example, proportional-integral control.

[0044] The PWM generating unit 73 generates gate signals for the upper arm switches QUH, QVH, and QWH based on the calculated duty ratio Duty. The gate signals are signals that instruct on control or off control. In this embodiment, the gate signals for the upper arm switches QUH, QVH, and QWH are synchronized.

[0045] The inverter 74 generates gate signals for the lower arm switches QUL, QVL, and QWL by inverting the logic of the gate signals for the upper arm switches QUH, QVH, and QWH generated by the PWM generating unit 73. In this embodiment, the gate signals for the lower arm switches QUL, QVL, and QWL are synchronized.

[0046] Figure 6 shows the transition of switching patterns etc. during heating PWM control. Figure 6(a) shows the transition of gate signals of the upper arm switches QUH, QVH, QWH, and Figure 6(b) shows the transition of gate signals of the lower arm switches QUL, QVL, QWL. Figure 6(c) shows the transition of current IR flowing to neutral point O and the transition of command current IM*. Figure 6(d) shows the transition of current IBH flowing to the first storage battery 21, and Figure 6(e) shows the transition of current IBL flowing to the second storage battery 22.

[0047] As shown in Fig. 6(a) and (b), a temperature rise PWM control is performed in which the upper arm switches QUH, QVH, and QWH and the lower arm switches QUL, QVL, and QWL are alternately turned on. This control continues until the temperature rise request in step S10 in Fig. 2 is no longer present. By this control, as shown in Fig. 6(d) and (e), a pulsed current flows through the first storage battery 21 and the second storage battery 22. During a period in which the command current IM* is positive, the first storage battery 21 is discharged and the second storage battery 22 is charged. On the other hand, during a period in which the command current IM* is negative, the second storage battery 22 is discharged and the first storage battery 21 is charged. The average values ​​IBHave and IBLave of the pulsed currents are sinusoidal currents that contain a component of the same frequency as the frequency of the command current IM*.

[0048] Simulation results of this embodiment are shown in Fig. 7. Fig. 7(a) to (c) correspond to Fig. 6(c) to (e), and Fig. 7(d) shows the transition of the terminal voltage of the capacitor 31. As shown in Fig. 7(d), the terminal voltage of the capacitor 31 does not fluctuate.

[0049] Figure 8 shows the results of a simulation of a comparative example having the configuration described in Patent Document 1. Figures 8(a) and (b) correspond to the above-mentioned Figures 7(a) and (d). Note that SK shown in Figures 8(b) and 7(d) is a symbol indicating the scale of the time axis.

[0050] As shown in Fig. 8(b), in the comparative example, the terminal voltage of the capacitor fluctuates greatly with the same period as the current IR flowing through the neutral point O. To reduce this fluctuation, it is necessary to increase the capacitance of the capacitor or reduce the amplitude of the command current IM*, i.e., the temperature rise capability.

[0051] According to the present embodiment described above in detail, the following effects can be obtained.

[0052] The intermediate terminal B and the neutral point O are connected by a connection path 60 without passing through each switch QUH to QWL of the inverter 30. In this configuration, the control device 70 performs switching control of the inverter 30 so that a ripple current flows between the first storage battery 21 and the second storage battery 22 through the inverter 30, each phase winding 41U, 41V, 41W, and the connection path 60. This makes it possible to reduce the amount of fluctuation in the terminal voltage of the capacitor 31 without increasing the frequency fc (=1 / Tc) of the reactive power (ripple current). Therefore, it is possible to reduce noise generated during the temperature rise control of the battery pack 20.

[0053] Furthermore, since the amount of fluctuation in the terminal voltage of the capacitor 31 can be reduced, the capacitance of the capacitor 31 can be reduced, and the capacitor 31 can be made smaller.

[0054] In the temperature rise control, the control device 70 synchronizes the switching control of the upper arm switches QUH, QVH, and QWH of all phases, and also synchronizes the switching control of the lower arm switches QUL, QVL, and QWL of all phases. This allows the windings 41U, 41V, and 41W of each phase to be regarded as equivalent circuits in which windings are connected in parallel. This makes it possible to reduce the inductance of the windings during the temperature rise control. This makes it possible to increase the amount of change in the current flowing to the neutral point O in one switching period Tsw, and allows the temperature rise control to be performed using a large current.

[0055] Moreover, by synchronizing the switching controls, the rotor of the rotating electrical machine 40 can be prevented from rotating.

[0056] When the control device 70 determines that there is a request to increase the temperature of the battery pack 20, it turns on the connection switch 61, and when it determines that there is no request to increase the temperature, it turns off the connection switch 61. This makes it possible to prevent a current from flowing from the neutral point O to the intermediate terminal B while the vehicle is running.

[0057] <Modification 1 of the First Embodiment> As shown in Fig. 9, two of the three phases may be on / off controlled to perform temperature rise PWM control. Fig. 9 shows an example in which the W-phase upper and lower arm switches QWH, QWL are maintained in off control. Fig. 9(a) shows the transition of the gate signals of the U- and V-phase upper arm switches QUH, QVH, Fig. 9(b) shows the transition of the gate signals of the U- and V-phase lower arm switches QUL, QVL, Fig. 9(c) shows the transition of the gate signals of the W-phase upper and lower arm switches QWH, QWL, and Figs. 9(d)-(f) correspond to Figs. 6(c)-(e) above.

[0058] Also, as shown in Fig. 10, one of the three phases may be on / off controlled to perform temperature rise PWM control. Fig. 10 shows an example in which only the U-phase upper and lower arm switches QUH, QUL are on / off controlled. Figs. 10(a) and (b) show the transitions of the gate signals of the U-phase upper arm switches QUH, QUL, Fig. 10(c) shows the transitions of the gate signals of the V-phase upper and lower arm switches QVH, QVL and the W-phase upper and lower arm switches QWH, QWL, and Figs. 10(d) to (f) correspond to Figs. 9(d) to (f) above.

[0059] Even with the switching control shown in FIG. 9 or FIG. 10, when the ripple current is small, the equivalent inductance of winding 41 may be increased to reduce the current ripple, and iron loss may be reduced more than when switching control of all phases is performed.

[0060] <Modification 2 of the First Embodiment> Instead of the configuration of FIG. 4, the switching control may be performed by the configuration shown in FIG. 11. In the control device 70, the hysteresis control unit 75 generates gate signals for the upper arm switches QUH, QVH, and QWH shown in FIG. 12(b) based on the command current IM* and the detected current IMr. More specifically, the hysteresis control unit 75 generates gate signals for the upper arm switches QUH, QVH, and QWH based on the current deviation between the command current IM* and the detected current IMr. The inverter 74 generates gate signals for the lower arm switches QUL, QVL, and QWL shown in FIG. 12(c) by inverting the logic of the gate signals for the upper arm switches QUH, QVH, and QWH generated by the hysteresis control unit 75. As a result, the detected current IMr is controlled within a range having a width of ±ΔI with respect to the command current IM* as shown in FIG. 12(a).

[0061] <Second embodiment> The second embodiment will be described below with reference to the drawings, focusing on the differences from the first embodiment.

[0062] In this embodiment, the control device 70 corrects the command current IM* so that the terminal voltage of the first storage battery 21 and the terminal voltage of the second storage battery 22 are equalized. In detail, the control device 70 calculates the terminal voltage VHr of the first storage battery 21 and the terminal voltage VLr of the second storage battery 22 based on the information transmitted from the monitoring unit 50. Then, when the control device 70 determines that the terminal voltage VHr of the first storage battery 21 is higher than the terminal voltage VLr of the second storage battery 22, the control device 70 calculates a corrected command current by adding a DC component Idc (>0) to the command current IM* as shown in FIG. 13. As a result, in the corrected command current for one period Tc, the area S1 of the first region becomes larger than the area S2 of the second region. As a result, in one period Tc, the discharge current of the first storage battery 21 exceeds the discharge current of the second storage battery 22, and the terminal voltage of the first storage battery 21 and the terminal voltage of the second storage battery 22 are equalized.

[0063] On the other hand, when the control device 70 determines that the terminal voltage VHr of the first storage battery 21 is lower than the terminal voltage VLr of the second storage battery 22, the control device 70 calculates a corrected command current by subtracting the DC component Idc from the command current IM* as shown in Fig. 14. As a result, in the corrected command current for one cycle Tc, the area S1 of the first region becomes smaller than the area S2 of the second region. As a result, in one cycle Tc, the discharge current of the second storage battery 22 exceeds the discharge current of the first storage battery 21, and the terminal voltages of the first storage battery 21 and the second storage battery 22 are equalized.

[0064] According to the present embodiment described above, the terminal voltage of the first storage battery 21 and the terminal voltage of the second storage battery 22 can be equalized while performing the temperature rise control.

[0065] <Modification of the second embodiment> The DC component Idc may be variably set based on the voltage difference between the terminal voltage VHr of the first storage battery 21 and the terminal voltage VLr of the second storage battery 22. Specifically, for example, when the terminal voltage VHr of the first storage battery 21 is higher than the terminal voltage VLr of the second storage battery 22, the DC component Idc may be set to be larger as "VHr-VLr" increases. Also, when the terminal voltage VHr of the first storage battery 21 is lower than the terminal voltage VLr of the second storage battery 22, the DC component Idc may be set to be larger as "VLr-VHr" increases.

[0066] In the correction process of the command current IM*, instead of the terminal voltage of each storage battery, for example, the lowest voltage among the terminal voltages of each battery cell constituting each storage battery, or the average value of the terminal voltages of each battery cell constituting each storage battery may be used.

[0067] <Third embodiment> The third embodiment will be described below with reference to the drawings, focusing on the differences from the first embodiment. In this embodiment, the control device 70 sets the switching frequency fsw (=1 / Tsw) when the rotating electric machine 40 is stopped to a frequency that is higher than the switching frequency of the upper and lower arm switches QUH to QWL when the rotating electric machine 40 is driven to rotate and the vehicle is running, and is in the inaudible range for humans.

[0068] Fig. 15 shows the procedure of the temperature rise control process according to this embodiment. This process is repeatedly executed by the control device 70, for example, at a predetermined control period. In Fig. 15, the same processes as those shown in Fig. 2 are denoted by the same reference numerals for convenience.

[0069] After completing the process of step S18, the process proceeds to step S20, where temperature rise PWM control is performed. Here, the switching frequency fsw of each of the switches QUH to QWL is set higher than the switching frequency set in the process of step S16. More specifically, the switching frequency fsw is set to a frequency of 16 kHz or higher, for example, a frequency in the inaudible range for humans (20 kHz or higher).

[0070] The temperature rise control is performed while the vehicle is stopped. In such a situation, the human hearing sensitivity to noise accompanying the switching control of the inverter 30 becomes high. Therefore, by setting the switching frequency fsw to a frequency of 16 kHz or more that is difficult for humans to hear and is not in the inaudible range, or to a frequency in the inaudible range, the NVH characteristics of the power conversion device 10 during the temperature rise control can be improved. Note that a frequency of 16 kHz or more is an excessively high frequency, and there is a concern that the switches QUH to QWL will generate heat due to switching loss. However, during the temperature rise control, the surroundings of the vehicle are in a low-temperature environment, so there is little risk that the temperature of each of the switches QUH to QWL will exceed its allowable upper limit.

[0071] <Fourth embodiment> In the first embodiment, the rotating electric machine and the inverter may be of a 5-phase or 7-phase or other phase than the 3-phase. Fig. 16 shows a power conversion device in the case of a 5-phase. In Fig. 16, the same components as those shown in Fig. 1 are denoted by the same reference numerals for convenience.

[0072] 16, X-phase upper and lower arm switches QXH, QXL and diodes DXH, DXL are added to the inverter 30, and Y-phase upper and lower arm switches QYH, QYL and diodes DYH, DYL are added to the inverter 30. An X-phase winding 41X and a Y-phase winding 41Y are added to the rotating electric machine 40. An X-phase conductive member 32X and a Y-phase conductive member 32Y are added to the power conversion device 10.

[0073] <Fifth embodiment> The fifth embodiment will be described below with reference to the drawings, focusing on the differences from the first embodiment.

[0074] A configuration diagram of a power conversion device in this embodiment is shown in Fig. 17. In Fig. 17, the same components as those shown in Fig. 1 are denoted by the same reference numerals for convenience.

[0075] In the configuration of the first embodiment shown in Fig. 1, the power conversion device 10 includes the connection path 60, the connection switch 61, and the current sensor 62. Instead of these configurations, in the present embodiment, the power conversion device 10 includes a connection path 90, a connection switch 91, and a current sensor 92. An intermediate terminal B of the battery pack 20 is connected to the emitter of the U-phase upper arm switch QUH and the collector of the U-phase lower arm switch QUL via the connection path 90. The connection switch 91 and the current sensor 92 are provided on the connection path 90.

[0076] In this embodiment, too, the control device 70 executes the temperature rise control process according to the procedure shown in Fig. 2. Here, the connection switch 61 in steps S13, S15, and S18 is replaced with a connection switch 91. The equivalent circuit of the power conversion device 10 used in the temperature rise PWM control of this embodiment is the same as the circuit shown in Fig. 3. Also, in the temperature rise control process of this embodiment, the method of switching control in the temperature rise PWM control of step S19 is changed. This control will be described below.

[0077] A block diagram of the heating PWM control in this embodiment is shown in Fig. 18. In Fig. 18, the configurations of the current deviation calculation unit 71 and the feedback control unit 72 and the method of setting the command current IM* are the same as those in the first embodiment, so the description will be omitted.

[0078] The PWM generating unit 73 generates gate signals for the V- and W-phase upper arm switches QVH and QWH based on the duty ratio Duty calculated by the feedback control unit 72. The inverter 74 generates gate signals for the V- and W-phase lower arm switches QVL and QWL by inverting the logic of the gate signals for the V- and W-phase upper arm switches QVH and QWH. In this embodiment, the U-phase upper and lower arm switches QUH and QUL are controlled to be turned off. Furthermore, switching controls of the V- and W-phase upper arm switches QVH and QWH are synchronized, and switching controls of the V- and W-phase lower arm switches QVL and QWL are synchronized.

[0079] Fig. 19 shows the transitions of the current IR etc. in this embodiment. Fig. 19(a) shows the transitions of the current IR flowing through the connection path 90, Fig. 19(b) shows the transitions of the current IBH flowing through the first storage battery 21, and Fig. 19(c) shows the transitions of the current IBL flowing through the second storage battery 22. Fig. 19(d) shows the transitions of the gate signals of the U-phase upper and lower arm switches QUH and QUL, Fig. 19(e) shows the transitions of the gate signals of the V- and W-phase upper arm switches QVH and QWH, and Fig. 19(d) shows the transitions of the gate signals of the V- and W-phase lower arm switches QVL and QWL.

[0080] In this embodiment, the U-phase upper and lower arm switches QUH and QUL are controlled to be turned off as shown in Fig. 19(d). Also, the V- and W-phase upper arm switches QVH and QWH and the V- and W-phase lower arm switches QVL and QWL are alternately controlled to be turned on as shown in Fig. 19(e) and (f). By this control, a pulsed current flows through the first storage battery 21 and the second storage battery 22 as shown in Fig. 19(b) and (c), and the current IR is controlled to the command current IM* as shown in Fig. 19(a).

[0081] Figure 20 shows the simulation results of this embodiment. Figures 20(a) to (c) correspond to the above-mentioned Figures 19(a) to (c), and Figure 20(d) shows the transition of the terminal voltage of the capacitor 31. As shown in Figure 20(d), the terminal voltage of the capacitor 31 does not fluctuate. SK shown in Figure 20(d) is a symbol indicating the scale of the time axis, and corresponds to SK shown in the above-mentioned Figure 8(b).

[0082] According to the present embodiment described above in detail, the following effects can be obtained.

[0083] An intermediate terminal B of the battery pack 20 is connected to the emitter of the U-phase upper arm switch QUH and the collector of the U-phase lower arm switch QUL via a connection path 90. In this configuration, the control device 70 performs switching control of the switches QUH to QWL so that a ripple current flows between the first storage battery 21 and the second storage battery 22 via the V- and W-phase upper and lower arm switches QVH, QWH, QVL, and QWL, the respective phase windings 41U, 41V, and 41W, and the connection path 90. This makes it possible to obtain the same effects as those of the first embodiment.

[0084] During temperature rise control, the control device 70 synchronizes the switching control of the V- and W-phase upper arm switches QVH and QWH, and also synchronizes the switching control of the V- and W-phase lower arm switches QVL and QWL. This allows the V- and W-phase windings 41V and 41W to be regarded as equivalent circuits in which windings are connected in parallel. This makes it possible to reduce the inductance of the windings during temperature rise control.

[0085] <Modification 1 of the Fifth Embodiment> Instead of the configuration in Fig. 18, switching control may be performed by the configuration shown in Fig. 21. In the control device 70, a hysteresis control unit 75 generates gate signals for the V- and W-phase upper arm switches QVH and QWH based on a command current IM* and a detected current IMr. An inverter 74 inverts the logic of the gate signals for the V- and W-phase upper arm switches QVH and QWH generated by the hysteresis control unit 75, thereby generating gate signals for the V- and W-phase lower arm switches QVL and QWL.

[0086] <Modification 2 of the Fifth Embodiment> The control device 70 may implement a temperature rise PWM control that controls the on / off of only one phase. Fig. 22 shows an example in which the W-phase upper and lower arm switches QWH, QWL are on / off controlled. Figs. 22(a)-(c) correspond to Figs. 19(a)-(c) above. Fig. 22(d) shows the transitions of the gate signals of the U- and V-phase upper and lower arm switches QUH, QUL, QVH, QVL, Fig. 22(e) shows the transitions of the gate signal of the W-phase upper arm switch QWH, and Fig. 22(f) shows the transitions of the gate signal of the W-phase lower arm switch QWL.

[0087] In this embodiment, the U-phase and V-phase upper and lower arm switches QUH, QUL, QVH, and QVL are turned off as shown in Fig. 22(d). Also, the W-phase upper arm switch QWH and the W-phase lower arm switch QWL are alternately turned on as shown in Fig. 22(e) and (f).

[0088] According to the switching control shown in FIG. 22, when the ripple current is small, the equivalent inductance of winding 41 is increased to reduce the current ripple, and iron loss can be reduced more than when V- and W-phase switching control is performed.

[0089] <Modification 3 of the fifth embodiment> The control device 70 may execute the temperature rise control according to the procedure shown in Fig. 15. In this case, after completing the process of step S18 in Fig. 15, the control device 70 proceeds to step S20 and executes the temperature rise PWM control. In this embodiment, the switching frequency fsw of the V- and W-phase upper and lower arm switches QVH, QWH, QVL, and QWL is set higher than the switching frequency set in the process of step S16. This makes it possible to obtain the same effect as the third embodiment.

[0090] <Modification 4 of the Fifth Embodiment> As described in the second embodiment, the control device 70 may correct the command current IM* so as to equalize the terminal voltage of the first storage battery 21 and the terminal voltage of the second storage battery 22. This makes it possible to obtain the same effects as those of the second embodiment.

[0091] <Fifth Modification of the Fifth Embodiment> The upper and lower arm switches connected to the intermediate terminal B of the battery pack 20 are not limited to the U-phase upper and lower arm switches QUH and QUL, but may be, for example, the V-phase upper and lower arm switches QVH and QVL. In this case, in the temperature rise control, the V-phase upper and lower arm switches QVH and QVL are controlled to be turned off. Also, the U- and W-phase upper arm switches QUH and QWH and the U- and W-phase lower arm switches QUL and QWL are controlled to be turned on alternately.

[0092] The upper and lower arm switches connected to the intermediate terminal B may be, for example, W-phase upper and lower arm switches QWH and QWL. In this case, in the temperature rise control, the W-phase upper and lower arm switches QWH and QWL are controlled to be turned off. Also, the U- and V-phase upper arm switches QUH and QVH and the U- and V-phase lower arm switches QUL and QVL are controlled to be turned on alternately.

[0093] Sixth Embodiment Hereinafter, the sixth embodiment will be described with reference to the drawings, focusing on the differences from the fifth embodiment. In this embodiment, the upper and lower arm switches connected to the intermediate terminal B of the battery pack 20 are not limited to one phase. It is sufficient that the intermediate terminal B is not connected to all the upper and lower arm switches of the U, V, and W phases.

[0094] 23 shows a configuration diagram of a power conversion device in which U-phase upper and lower arm switches QUH, QUL and W-phase upper and lower arm switches QWH, QWL are connected to an intermediate terminal B of the battery pack 20. In this embodiment, the intermediate terminal B of the battery pack 20 is connected to the emitter of the U-phase upper arm switch QUH and the collector of the U-phase lower arm switch QUL via a U-phase connection path 90U. In addition, the intermediate terminal B of the battery pack 20 is connected to the emitter of the W-phase upper arm switch QWH and the collector of the W-phase lower arm switch QWL via a W-phase connection path 90W.

[0095] In this embodiment, when the temperature rise PWM control is performed, the U- and W-phase upper and lower arm switches QUH, QUL, QWH, and QWL are controlled to be turned off, and the V-phase upper arm switch QVH and the V-phase lower arm switch QVL are alternately controlled to be turned on.

[0096] According to the present embodiment described above, it is possible to obtain the same effects as those of the fifth embodiment.

[0097] Seventh embodiment In the fifth embodiment, the rotating electric machine and the inverter may be of a five-phase or seven-phase type other than three-phase type as described in the fourth embodiment. Fig. 24 shows a power conversion device in the case of a five-phase type. In Fig. 24, the same components as those shown in Fig. 17 are denoted by the same reference numerals for convenience.

[0098] <Other embodiments> Each of the above embodiments may be modified as follows.

[0099] The location of the current sensor that detects the current flowing through the neutral point O is not limited to the example shown in Fig. 1. For example, a current sensor may be provided in each of the conductive members 32U, 32V, and 32W in Fig. 1. In this case, during temperature rise control, the total value of the currents detected by the current sensors in each of the conductive members 32U, 32V, and 32W may be set as the detected current IMr.

[0100] The method of setting the command current IM* is not limited to that shown in Fig. 5. For example, the positive command current IM* and the negative command current IM* may be set to a trapezoidal wave or a square wave, respectively, as long as the positive command current IM* and the negative command current IM* are point-symmetric with respect to the zero-cross timing of the command current IM* in one cycle Tc.

[0101] Furthermore, the method of setting the command current IM* is not limited to the one that satisfies the point-symmetric relationship. For example, the command current IM* may be set so that the period from the zero-up cross timing to the zero-down cross timing of the command current IM* in one cycle Tc is different from the period from the zero-down cross timing to the zero-up cross timing of the command current IM*, and the area S1 of the first region is equal to the area S2 of the second region. Even in this case, the balance of the charge and discharge currents of the first storage battery 21 and the second storage battery 22 in one cycle Tc can be matched.

[0102] The number of battery cells may be different between the first storage battery 21 and the second storage battery 22. In this case, the terminal voltage of the first storage battery 21 and the terminal voltage of the second storage battery 22 will be different, and the intermediate terminal B will be provided at a position that does not equally divide the battery cells constituting the battery pack 20.

[0103] In the first embodiment, the control device 70 does not have to synchronize the switching control of the upper arm switches QUH, QVH, QWH of all phases during temperature rise control, and also does not have to synchronize the switching control of the lower arm switches QUL, QVL, QWL of all phases.

[0104] The connection switch 61 is not limited to a relay. For example, a pair of N-channel MOSFETs with their sources connected to each other, or an IGBT may be used as the connection switch 61.

[0105] In the first to fourth embodiments, the connection switch 61 is not essential. In this case, the intermediate terminal B and the neutral point O are electrically connected at all times.

[0106] The upper and lower arm switches constituting the inverter are not limited to IGBTs, but may be, for example, N-channel MOSFETs. In this case, the high-potential terminal is the drain, and the low-potential terminal is the source.

[0107] The first storage battery and the second storage battery do not have to constitute a battery pack.

[0108] The control unit and the method described in the present disclosure may be realized by a special-purpose computer provided by configuring a processor and a memory programmed to execute one or more functions embodied in a computer program. Alternatively, the control unit and the method described in the present disclosure may be realized by a special-purpose computer provided by configuring a processor with one or more dedicated hardware logic circuits. Alternatively, the control unit and the method described in the present disclosure may be realized by one or more special-purpose computers configured by a combination of a processor and a memory programmed to execute one or more functions and a processor configured with one or more hardware logic circuits. In addition, the computer program may be stored in a computer-readable non-transitory tangible recording medium as instructions executed by a computer. [Explanation of symbols]

[0109] 10...power conversion device, 20...battery pack, 30...inverter, 31...capacitor, 40...rotating motor, 41U, 41V, 41W...U, V, W phase windings, 60, 90...connection path, 61...connection switch, 90U...U phase connection path, 90W...W phase connection path, 70...control device, QUH, QVH, QWH...U, V, W phase upper arm switches, QUL, QVL, QWL...U, V, W phase lower arm switches.

Claims

1. A power conversion device (10) that is electrically connectable to polyphase windings (41U, 41V, 41W, 41X, 41Y) of a rotating electric machine (40), a first storage battery (21), and a second storage battery (22), and that is electrically connectable between a negative electrode side of the first storage battery and a positive electrode side of the second storage battery and a neutral point (O) of the windings of each phase by a connection path (60), an inverter (30) having upper arm switches (QUH, QVH, QWH, QXH, QYH) and lower arm switches (QUL, QVL, QWL, QXL, QYL) connected in series for the number of phases; a control unit (70) that performs control processing to synchronize switching controls of the upper arm switches of all phases and synchronize switching controls of the lower arm switches of all phases so that a current flows between the first storage battery and the second storage battery via the inverter, the winding, and the connection path, A capacitor (31) is connected in parallel to the series connection of the upper arm switch and the lower arm switch.

2. The winding is a three-phase winding, The power conversion device according to claim 1 , wherein the inverter has three phases of series-connected upper arm switches and lower arm switches.

3. The winding is a five-phase winding, The power conversion device according to claim 1 , wherein the inverter has five phases of series-connected upper arm switches and lower arm switches.

4. The winding is a seven-phase winding, The power conversion device according to claim 1 , wherein the inverter has seven phases of series-connected upper arm switches and lower arm switches.

5. A high-potential side terminal of the upper arm switch of each phase can be electrically connected to a positive electrode side of the first storage battery, A low potential side terminal of the lower arm switch of each phase can be electrically connected to a negative electrode side of the second storage battery, A power conversion device as described in any one of claims 1 to 4, wherein in each phase, the low potential side terminal of the upper arm switch and the high potential side terminal of the lower arm switch are electrically connectable to the ends of the winding opposite the neutral point.

6. A power conversion device as described in any one of claims 1 to 5, wherein the control unit sets the command value so that, during one period of the command value of the current to be flowed through the connection path, an area specified by a positive command value and an area specified by a negative command value appear, and performs the control processing to control the current flowing through the connection path to the set command value.

7. A power conversion device as described in any one of claims 1 to 5, wherein the control unit sets a command value for the current to be flowed through the connection path to be sinusoidal, and performs the control processing to control the current flowing through the connection path to the set command value.

8. A power conversion device as described in any one of claims 1 to 5, wherein the control unit sets the command value so that, during one period of the command value for the current to flow through the connection path, the area of ​​the region specified by the positive command value is equal to the area of ​​the region specified by the negative command value, and performs the control processing to control the current flowing through the connection path to the set command value.

9. A power conversion device as described in any one of claims 6 to 8, wherein the control unit sets the command value so that the positive command value and the negative command value are point-symmetric with respect to the zero-crossing timing of the command value during one period of the command value.

10. A voltage information detection unit (50) for detecting voltage information of the first storage battery and the second storage battery, The control unit corrects the command value based on the detected voltage information so that the terminal voltage of the first storage battery and the terminal voltage of the second storage battery are equalized. The power conversion device according to any one of claims 6 to 9.

11. A power conversion device as described in any one of claims 1 to 10, wherein the connection path is provided with a connection switch (61) which, when turned on, electrically connects the negative electrode side of the first storage battery and the positive electrode side of the second storage battery to the neutral point, and when turned off, electrically disconnects the negative electrode side of the first storage battery and the positive electrode side of the second storage battery from the neutral point.

12. The power conversion device described in Claim 11, wherein the control unit turns the connection switch on when it determines that there is a request to increase the temperature of the first storage battery and the second storage battery, and turns the connection switch off when it determines that there is no request to increase the temperature.

13. A power conversion device as described in Claim 12, wherein when the control unit determines that there is no request to increase the temperature and that there is a request to drive the rotating electric machine, it turns off the connection switch and performs switching control of the upper arm switch and the lower arm switch to drive the rotating electric machine in rotation.

14. A power conversion device as described in claim 12 or 13, wherein when the control unit determines that there is no request to increase the temperature and that there is no request to drive the rotating motor, it turns off the connection switch and turns off the upper arm switch and the lower arm switch.

15. A power conversion device as described in any one of claims 1 to 14, wherein the control unit sets the switching frequency of the control processing when the driving of the rotating electric machine is stopped to a frequency higher than the switching frequency of the upper and lower arm switches when the rotating electric machine is driven.

16. A power conversion device described in any one of claims 1 to 15, wherein the control unit performs the control processing when the rotating motor is not driven.

17. A program applied to a power conversion device (10) that is electrically connectable to polyphase windings (41U, 41V, 41W, 41X, 41Y) of a rotating electric machine (40), a first storage battery (21), and a second storage battery (22), and that is electrically connectable between a negative electrode side of the first storage battery and a positive electrode side of the second storage battery and a neutral point (O) of the windings of each phase by a connection path (60), The power conversion device includes an inverter (30) having a number of series-connected upper arm switches (QUH, QVH, QWH, QXH, QYH) and lower arm switches (QUL, QVL, QWL, QXL, QYL) corresponding to the number of phases, A capacitor (31) is connected in parallel to the series connection of the upper arm switch and the lower arm switch, A program that causes a computer (70) to execute a control process that synchronizes the switching control of the upper arm switches of all phases and synchronizes the switching control of the lower arm switches of all phases so that current flows between the first storage battery and the second storage battery via the inverter, the winding, and the connection path.

18. A control method for a power conversion device (10) that is applied to a power conversion device that is electrically connectable to polyphase windings (41U, 41V, 41W, 41X, 41Y) of a rotating electric machine (40), a first storage battery (21), and a second storage battery (22), and that is electrically connectable between a negative electrode side of the first storage battery and a positive electrode side of the second storage battery and a neutral point (O) of the windings of each phase by a connection path (60), The power conversion device includes an inverter (30) having a number of series-connected upper arm switches (QUH, QVH, QWH, QXH, QYH) and lower arm switches (QUL, QVL, QWL, QXL, QYL) corresponding to the number of phases, A capacitor (31) is connected in parallel to the series connection of the upper arm switch and the lower arm switch, A control method for a power conversion device, comprising a control step of synchronizing switching control of the upper arm switches of all phases and synchronizing switching control of the lower arm switches of all phases so that current flows between the first storage battery and the second storage battery via the inverter, the winding, and the connection path.

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