Power conversion device

Abstract

A power conversion device (11) includes a rotating electrical machine (40) and an inverter (30). The power conversion device is provided with: connection switches (61a, 61b) which are provided in the connection path (60) and which electrically connect the negative electrode side of the first storage battery (21) and the positive electrode side of the second storage battery (22) to the neutral points of the star-connected windings (41U, 41V, 41W) by being turned on, and which electrically connect the negative electrode side of the first storage battery (21) and the positive electrode side of the second storage battery (22) to the neutral points of the star-connected windings (41U, 41V, 41W) by being turned off; electrically disconnecting the negative electrode side of the first storage battery and the positive electrode side of the second storage battery from the neutral point; a control unit (70) that performs switching control of the upper arm switches (QUH, QVH, QWH) and the lower arm switches (QUL, QVL, QWL) while turning on the connection switches; a determination unit (73, 81) that determines whether or not to perform short-circuit control for turning on one of the upper arm switch and the lower arm switch and turning off the other one of the upper arm switch and the lower arm switch; and a cut-off unit (86) that turns off the connection switch when it is determined that the short-circuit control is to be performed.

Description

Citation of related applications

[0001] This application is based on Japanese Patent Application No. 2022-122122 filed on July 29, 2022, and the contents thereof are incorporated herein by reference. Technical Field

[0002] The present disclosure relates to a power conversion device. Background Art

[0003] As a power conversion device, a power conversion device including a rotating electric machine having a winding and an inverter having a series connection of an upper arm switch and a lower arm switch is known. For example, in the power conversion device described in Patent Document 1, there is described a power conversion device including a connection path that electrically connects the negative electrode side of a first storage battery and the positive electrode side of a second storage battery to the neutral point of the winding and a connection switch provided in the connection path. The power conversion device performs temperature increase control to increase the temperature of the first storage battery and the second storage battery when the connection switch is turned on. Prior art literature Patent Literature

[0004] Patent Document 1: Japanese Patent Application Publication No. 2021-93845 Summary of the invention

[0005] For example, when the connection switch is turned on, in the event of an abnormality in the power conversion device, short-circuit control is sometimes performed to turn on one of the upper arm switch and the lower arm switch and disconnect the other. Short-circuit control is performed to prevent the back electromotive force generated in the winding due to the rotation of the rotor in the rotating electrical machine from being applied to the first battery and the second battery and causing an overvoltage abnormality. However, if short-circuit control is performed with the connection switch turned on, the back electromotive force generated in the winding may be applied to the first battery or the second battery via the connection path. Therefore, the reliability of the first battery and the second battery may be reduced.

[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 capable of suppressing a decrease in reliability of a first storage battery and a second storage battery connected in series.

[0007] The present invention discloses an electric power conversion device, which includes: a rotating electric machine having a star-connected winding; and an inverter having a series connection of an upper arm switch and a lower arm switch, wherein the electric power conversion device includes: a connection path, which electrically connects the negative electrode side of the first battery and the positive electrode side of the second battery in a first battery and a second battery connected in series to the neutral point of the winding; and a connection switch, which is arranged in the connection path and is set to be turned on to connect the negative electrode side of the first battery to the positive electrode side of the second battery. and the positive electrode side of the second battery is electrically connected to the neutral point, and the negative electrode side of the first battery and the positive electrode side of the second battery are electrically disconnected from the neutral point by being set to be disconnected; a control unit, which controls the switching of the upper arm switch and the lower arm switch while turning on the connecting switch; a determination unit, which determines whether to perform a short-circuit control in which either the upper arm switch or the lower arm switch is turned on and the other is disconnected; and a disconnection unit, which disconnects the connecting switch when it is determined that the short-circuit control is to be performed.

[0008] When the connection switch is turned on, the upper arm switch and the lower arm switch are sometimes switched on and off. In this case, for example, if it is determined during the implementation of the switch control that short-circuit control is performed due to an abnormality in the power conversion device, short-circuit control may be performed when the connection switch is turned on.

[0009] Therefore, when the determination unit determines that short-circuit control is to be performed, the connection switch is turned off. Thus, the period during which short-circuit control is performed while the connection switch is turned on can be suppressed. Therefore, the back electromotive force generated in the winding can be suppressed from being applied to at least one of the first storage battery and the second storage battery. As a result, the first storage battery and the second storage battery can be suppressed from becoming overvoltage states, and the reliability of the first storage battery and the second storage battery can be suppressed from being reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] 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 the power conversion system according to the first embodiment. Figure 2 : is a flowchart showing the processing steps of the switch control. Figure 3 It is a diagram showing a control circuit and its peripheral structure. Figure 4 : is a timing chart showing the transition of the phase current in the comparative example. Figure 5 It is a diagram showing an example of a current path in a comparative example. Figure 6 It is a timing chart showing the procedure of the shutoff control. Figure 7 It is a timing chart showing the transition of phase current. Figure 8 It is a timing chart showing an example of a current path. Fig. 9 It is a configuration diagram of a power conversion system according to a second embodiment. Fig.10 This is a timing chart showing an example of control before and after the three-phase short-circuit control is performed. Fig.11 It is a configuration diagram of a power conversion system according to a third embodiment. Fig.12 : is a flowchart showing the processing steps of the switch control. Fig.13 This is a flowchart showing a process procedure of switch control according to a modification of the third embodiment. Fig.14 It is a diagram showing a control circuit and its peripheral configuration according to a fourth embodiment. Fig.15 This is a flowchart of the processing executed by the determination unit. Fig.16 It is a diagram showing a connection path and its surrounding structure according to another embodiment. Fig.17 It is a diagram showing a connection path and its surrounding structure according to another embodiment. Fig.18 It is a diagram showing a connection path and its surrounding structure according to another embodiment. Fig.19 It is a diagram showing a connection path and its surrounding structure according to another embodiment. Fig. 20 It is a diagram showing a connection path and its surrounding structure according to another embodiment. Fig.21 It is a diagram showing a connection path and its surrounding structure according to another embodiment. Fig. 22 It is a diagram showing a connection path and its surrounding structure according to another embodiment. Fig.23 It is a diagram showing a connection path and its surrounding structure according to another embodiment. Fig.24 It is a diagram showing a connection path and its surrounding structure according to another embodiment. Fig.25 It is a diagram showing a connection path and its surrounding structure according to another embodiment. Fig.26 It is a diagram showing a connection path and its surrounding structure according to another embodiment. Fig. 27 It is a diagram showing a connection path and its surrounding structure according to another embodiment. DETAILED DESCRIPTION

[0011] <First embodiment> Hereinafter, a first embodiment of the power conversion device of the present disclosure will be described with reference to the drawings. The power conversion system of this embodiment is installed in a vehicle such as an electric vehicle or a hybrid vehicle.

[0012] like Figure 1 As shown, the power conversion system 10 includes a power conversion device 11 and a battery pack 20. The battery pack 20 is configured as a series connection of battery cells as single batteries, and the terminal voltage is, for example, several hundred V. In the present embodiment, the terminal voltages (for example, rated voltages) of the battery cells constituting the battery pack 20 are set to be the same as each other. As the battery cells, for example, secondary batteries such as lithium-ion batteries can be used. In addition, the battery pack 20 is, for example, provided outside the power conversion device 11.

[0013] The power conversion device 11 includes an inverter 30 and a rotating electric machine 40. The rotating electric machine 40 is a three-phase synchronous machine, and as a stator winding, includes a U-phase winding 41U, a V-phase winding 41V, and a W-phase winding 41W connected in star connection. Each phase winding 41U, 41V, and 41W is arranged in a manner that each is staggered by 120 degrees in electrical angle. The rotating electric machine 40 is, for example, a permanent magnet synchronous machine. In the present embodiment, the rotating electric machine 40 is a vehicle-mounted main machine and is a driving power source for the vehicle.

[0014] The inverter 30 has a switch device section 31. The switch device section 31 has a series connection body of a U-phase upper arm switch QUH, a V-phase upper arm switch QVH, a W-phase upper arm switch QWH and a U-phase lower arm switch QUL, a V-phase lower arm switch QVL, and a W-phase lower arm switch QWL corresponding to three. In the present embodiment, as each switch QUH, QVH, QWH, QUL, QVL, QWL, a voltage-controlled semiconductor switch element is used, specifically, an IGBT is used. Therefore, the high potential side terminal of each switch QUH, QVH, QWH, QUL, QVL, QWL is a collector, and the low potential side terminal is an emitter. For each switch QUH, QVH, QWH, QUL, QVL, QWL, each diode DUH, DVH, DWH, DUL, DVL, DWL as a freewheeling diode is connected in reverse parallel.

[0015] The emitter of the U-phase upper arm switch QUH and the collector of the U-phase lower arm switch QUL are connected to the first end of the U-phase winding 41U via a U-phase conductive component 33U such as a busbar. The emitter of the V-phase upper arm switch QVH and the collector of the V-phase lower arm switch QVL are connected to the first end of the V-phase winding 41V via a V-phase conductive component 33V such as a busbar. The emitter of the W-phase upper arm switch QWH and the collector of the W-phase lower arm switch QWL are connected to the first end of the W-phase winding 41W via a W-phase conductive component 33W such as a busbar. The second ends of the U-phase winding 41U, the V-phase winding 41V, and the W-phase winding 41W are connected to each other at the neutral point O. In addition, in the present embodiment, the number of turns of each phase winding 41U, 41V, and 41W is set to be the same. As a result, the inductance of each phase winding 41U, 41V, and 41W is set to be the same.

[0016] The collector of each upper arm switch QUH, QVH, QWH is connected to the positive terminal of the battery pack 20 through a positive-side bus bar Lp such as a bus bar. The emitter of each lower arm switch QUL, QVL, QWL is connected to the negative terminal of the battery pack 20 through a negative-side bus bar Ln such as a bus bar. A positive-side disconnect switch 23 is provided in the positive-side bus bar Lp, and a negative-side disconnect switch 24 is provided in the negative-side bus bar Ln. Each disconnect switch 23, 24 is, for example, a mechanical relay or a semiconductor switch element.

[0017] In the present embodiment, the control device 70 turns each disconnect switch 23, 24 on and off according to whether the power conversion system 10 is started. For example, the control device 70 is configured to be able to input a signal notifying that the start switch 51 is turned on or off. The start switch 51 is, for example, an ignition switch or a push-type start switch, and is operated by a user of the vehicle. When the start switch 51 is turned on by the user, the control device 70 starts the power conversion system 10. In this case, each disconnect switch 23, 24 is turned on. On the other hand, when the start switch 51 is turned off by the user, the control device 70 stops the power conversion system 10. In this case, each disconnect switch 23, 24 is turned off. In addition, each disconnect switch 23 can also be turned on and off by a control device higher than the control device 70.

[0018] The power conversion device 11 includes a smoothing capacitor 32 that connects the positive-side bus line Lp and the negative-side bus line Ln. The smoothing capacitor 32 may be built in the inverter 30 or provided outside the inverter 30.

[0019] Among the battery cells constituting the battery pack 20, a plurality of battery cells connected in series on the high potential side constitutes a first storage battery 21, and a plurality of battery cells connected in series on the low potential side constitutes a second storage battery 22. That is, the battery pack 20 is divided into two blocks. In the battery pack 20, the negative terminal of the first storage battery 21 and the positive terminal of the second storage battery 22 are connected via the intermediate terminal B. In the present 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.

[0020] The power conversion device 11 includes a monitoring unit 50. The monitoring unit 50 detects the terminal voltage and temperature of each battery cell constituting the battery pack 20, and monitors the state of the battery pack 20. In the present embodiment, the monitoring unit 50 can communicate with the control device 70 included in the power conversion device 11. The monitoring unit 50 detects the terminal voltage VB of the battery pack 20, the terminal voltage VH of the first storage battery 21, and the terminal voltage VL of the second storage battery 22, and these detection values ​​are input to the control device 70.

[0021] The power conversion device 11 includes a connection path 60 and a connection switch 61a. The connection path 60 electrically connects the intermediate terminal B of the battery pack 20 to the neutral point O. The connection switch 61a is a switch provided in the connection path 60 and switches on and off the current flowing in the connection path 60. In the present embodiment, a mechanical relay is used as the connection switch 61a. By turning on the connection switch 61a, the intermediate terminal B is electrically connected to the neutral point O. On the other hand, by turning off the connection switch 61a, the intermediate terminal B is electrically disconnected from the neutral point O. The connection switch 61a is driven by the control device 70.

[0022] The power conversion device 11 includes a phase current sensor 62, a neutral point current sensor 63, and an angle sensor 64. The phase current sensor 62 detects each phase current Iu, Iv, Iw flowing in each conductive member 33U to 33W. The neutral point current sensor 63 detects the neutral point current IMr flowing through the neutral point O. The angle sensor 64 is, for example, a resolver, and the angle sensor 64 detects the rotation angle θ (for example, electrical angle) of the rotor of the rotating electric machine 40. The detection values ​​of the phase current sensor 62, the neutral point current sensor 63, and the angle sensor 64 are input to the control device 70.

[0023] The power conversion system 10 includes an acceleration sensor 52 and a leakage detection device 53. The acceleration sensor 52 detects the acceleration ar of the vehicle. The detection value of the acceleration sensor 52 is input to the control device 70.

[0024] The leakage detection device 53 includes a coupling capacitor 53a, a resistor 53b, an oscillating portion 53c, and a detecting portion 53d, and detects leakage of a high-voltage circuit including the battery pack 20, the inverter 30, and the rotating electric machine 40. The high-voltage circuit is electrically insulated from the ground. Figure 1 In FIG. 1 , the insulation state between the negative-side bus bar Ln of the inverter 30 and the grounding member and between the W-phase conductive member 33W and the grounding member is represented by the insulation resistance RL. The leakage of the high-voltage circuit is caused by the flow of current through the insulation resistance RL between the high-voltage circuit and the grounding member. In addition, the grounding member is, for example, a body grounding member composed of a metal body frame of a vehicle.

[0025] The coupling capacitor 53a is connected to the negative terminal of the second battery 22 to insulate the DC component. The resistor 53b is connected in series with the coupling capacitor 53a on the side opposite to the second battery 22 and is connected in series with the oscillator 53c. The detector 53d is connected to the connection point between the coupling capacitor 53a and the resistor 53b.

[0026] The leakage detection device 53 performs a leakage detection operation of the high voltage circuit when the vehicle is parked. In the leakage detection operation, the oscillating unit 53c generates a pulse voltage (i.e., an AC voltage) of a specified frequency, and applies the pulse voltage of the specified frequency to the resistor 53b. The detection unit 53d detects the voltage to ground at the connection point between the coupling capacitor 53a and the resistor 53b. The voltage to ground is a voltage obtained by dividing the AC voltage applied to the resistor 53b by the resistance value of the resistor 53b and the insulation resistance RL of the high voltage circuit. In addition, the detection unit 53d determines whether the high voltage circuit has leakage based on the detected voltage to ground. In addition, the leakage detection device 53 is not limited to performing a leakage detection operation when the vehicle is parked, and can also perform a leakage detection operation when the vehicle is driving.

[0027] When the leakage detection operation of the high voltage circuit is performed, the detection unit 53 d outputs a signal Sge indicating that the leakage detection operation is performed. The signal Sge indicating that the leakage detection operation is performed is input to the control device 70 .

[0028] The control device 70 implements various control functions by executing programs stored in a storage device included in the control device 70. The various control functions may be implemented by an electronic circuit as hardware, or by both hardware and software.

[0029] Hereinafter, a description will be given of switching control of the switches QUH to QWL constituting the inverter 30. In the present embodiment, the switching control includes motor drive control, temperature increase control, and temperature increase motor drive control.

[0030] As the switching control, the control device 70 performs motor drive control to feedback control the control amount of the rotary electric machine 40 to its command value. The control amount of the motor drive control is, for example, torque. In this case, in each phase, the upper arm switch and the lower arm switch are alternately turned on.

[0031] As a switch control, the control device 70 performs temperature increase control to increase the temperature of the battery pack 20. In the temperature increase control, when the connection switch 61a is turned on, each switch QUH to QWL is turned on and off so that an AC current flows between the first storage battery 21 and the second storage battery 22 via the switch device unit 31, each phase winding 41U, 41V, 41W and the connection path 60. As a result, power is transmitted between the first storage battery 21 and the second storage battery 22, and the transmitted power is converted into heat energy in each storage battery 21, 22. The converted heat energy is used to increase the temperature of the battery pack 20.

[0032] As the switch control, the control device 70 performs temperature increase motor drive control. The temperature increase motor drive control is a control to increase the temperature of the battery pack 20 while feedback controlling the control amount of the rotating electric machine 40 to its command value. That is, in the temperature increase motor drive control, the temperature increase control is performed while performing the motor drive control.

[0033] Here, use Figure 2 Next, a description will be given of a process procedure of the switch control executed by the controller 70. This control is repeatedly executed by the control device 70 at a predetermined control cycle, for example.

[0034] In step S10, it is determined whether there is a request for temperature increase of the first storage battery 21 and the second storage battery 22. In the present embodiment, when it is determined that the temperature of the battery pack 20 is lower than the target temperature, it is determined that there is a request for temperature increase. Here, the temperature of the battery pack 20 may be acquired from the monitoring unit 50. In addition, as the temperature of the battery pack 20, the temperature of the first storage battery 21, the temperature of the second storage battery 22, or the average temperature of the first storage battery 21 and the second storage battery 22 may be used.

[0035] If it is determined in step S10 that there is no temperature increase request, the process proceeds to step S11 to determine whether there is a drive request for the rotating electric machine 40. The drive request for the rotating electric machine 40 is a drive request for rotating the rotor of the rotating electric machine 40. Whether there is a drive request for the rotating electric machine 40 may be determined based on, for example, a torque command value transmitted from a higher-level control device to the control device 70.

[0036] If it is determined in step S11 that there is no drive request for the rotary electric machine 40, the process proceeds to step S12 and the standby control is performed. In the standby control, the switches QUH to QWL of the inverter 30 are turned off. Then, in step S13, the connection switch 61a is turned off. As a result, the intermediate terminal B and the neutral point O are electrically disconnected.

[0037] If it is determined in step S11 that there is a drive request for the rotary electric machine 40, the process proceeds to step S14 to perform motor drive control. Then, in step S15, the connection switch 61a is turned off. As a result, the intermediate terminal B and the neutral point O are electrically disconnected.

[0038] In step S16, PWM processing is performed. PWM processing is a process for generating switching commands for each switch QUH to QWL based on the comparison of the U-phase modulation rate, the V-phase modulation rate, and the W-phase modulation rate with the carrier signal (e.g., a triangular wave signal). In the PWM processing of the motor drive control, the U-phase modulation rate, the V-phase modulation rate, and the W-phase modulation rate are calculated based on the torque command value of the rotating electric machine 40.

[0039] Specifically, the torque command value of the rotary electric machine 40 output from the upper control device to the control device 70 is obtained. The d-axis command current and the q-axis command current are set based on the torque command value of the rotary electric machine 40. In addition, the detection value of the phase current sensor 62 and the detection value of the angle sensor 64 are obtained. The d-axis current and the q-axis current are calculated based on the detection value of the phase current sensor 62 and the detection value of the angle sensor 64.

[0040] The d-axis command voltage is calculated as the operation amount for feedback-controlling the d-axis current to the d-axis command current. The q-axis command voltage is calculated as the operation amount for feedback-controlling the q-axis current to the q-axis command current. The feedback control is, for example, proportional-integral control.

[0041] The d-axis command voltage and the q-axis command voltage are converted into the U-phase command voltage, the V-phase command voltage, and the W-phase command voltage in the three-phase fixed coordinate system based on the detection value of the angle sensor 64. The U-phase command voltage, the V-phase command voltage, and the W-phase command voltage become waveforms whose phases are shifted by 120 degrees electrical angle.

[0042] The U-phase final command voltage is calculated by adding the U-phase command voltage to the offset correction amount. The offset correction amount is the command voltage added to the U-phase command voltage, the V-phase command voltage, and the W-phase command voltage when performing temperature rise control. In the motor drive control, the offset correction amount is 0. That is, in the motor drive control, the U-phase final command voltage, the V-phase final command voltage, and the W-phase final command voltage are the U-phase command voltage, the V-phase command voltage, and the W-phase command voltage. In the same way as the case of calculating the U-phase final command voltage, the V-phase final command voltage is calculated by adding the V-phase command voltage to the offset correction amount. In addition, the W-phase final command voltage is calculated by adding the W-phase command voltage to the offset correction amount. In addition, the calculation method of the offset correction amount will be described later.

[0043] The U-phase modulation rate, the V-phase modulation rate, and the W-phase modulation rate are calculated by dividing the U-phase final command voltage, the V-phase final command voltage, and the W-phase final command voltage by the power supply voltage. The power supply voltage is, for example, 1 / 2 of the total value of the terminal voltage VB of the battery pack 20 acquired from the monitoring unit 50.

[0044] If it is determined in step S10 that there is a temperature increase request, the process proceeds to step S17. In step S17, similarly to the process in step S11, it is determined whether there is a drive request for the rotary electric machine 40.

[0045] If it is determined in step S17 that there is no drive request for the rotary electric machine 40 , the process proceeds to step S18 to perform temperature increase control. Then, in step S19 , the connection switch 61 a is turned on. As a result, the intermediate terminal B and the neutral point O are electrically connected via the connection path 60 .

[0046] In step S20 , a PWM process is performed. In the PWM process of the temperature increase control, the U-phase modulation rate, the V-phase modulation rate, and the W-phase modulation rate are calculated based on the target temperature of the battery pack 20 .

[0047] Specifically, the target temperature of the battery pack 20 outputted from the upper control device to the control device 70 is obtained. The neutral point command current is set based on the target temperature of the battery pack 20. The waveform of the neutral point command current is set to a sine wave, for example. At this time, the larger the deviation between the target temperature of the battery pack 20 and the temperature of the battery pack 20 is, the larger the amplitude of the neutral point command current may be set.

[0048] The detection value of the neutral point current sensor 63 is acquired. The offset correction amount is calculated as an operation amount for feedback control of the detection value of the neutral point current sensor 63 as a neutral point command current. The feedback control is, for example, proportional integral control.

[0049] The process of calculating the U-phase modulation rate, V-phase modulation rate, and W-phase modulation rate is the same as that in the case of motor drive control. However, in temperature rise control, since the U-phase command voltage, V-phase command voltage, and W-phase command voltage are 0, the U-phase final command voltage, V-phase final command voltage, and W-phase final command voltage are offset correction amounts. The U-phase modulation rate, V-phase modulation rate, and W-phase modulation rate are calculated by dividing the offset correction amount by the power supply voltage.

[0050] If it is determined in step S17 that there is a drive request for the rotary electric machine 40, the process proceeds to step S21, and the temperature increase motor drive control is performed. Then, in step S22, the connection switch 61a is turned on.

[0051] In step S23, PWM processing is performed. In the PWM processing of the temperature rise motor drive control, the U-phase modulation rate, the V-phase modulation rate, and the W-phase modulation rate are calculated based on the torque command value of the rotating motor 40 and the target temperature of the battery pack 20. Specifically, the U-phase final command voltage is calculated by adding the U-phase command voltage to the offset correction amount. The V-phase final command voltage is calculated by adding the V-phase command voltage to the offset correction amount. The W-phase final command voltage is calculated by adding the W-phase command voltage to the offset correction amount. The U-phase modulation rate, the V-phase modulation rate, and the W-phase modulation rate are calculated by dividing the U-phase final command voltage, the V-phase final command voltage, and the W-phase final command voltage by the power supply voltage. In addition, the calculation method of the U-phase command voltage, the V-phase command voltage, and the W-phase command voltage is the same as that of the motor drive control. In addition, the calculation method of the offset correction amount is the same as that of the temperature rise control.

[0052] Next, the three-phase short-circuit control performed by the control device 70 will be described. The three-phase short-circuit control is a control in which one of the upper arm switches QUH to QWH and the lower arm switches QUL to QWL is turned on and the other is turned off. The three-phase short-circuit control is performed to suppress the back electromotive force generated in each phase winding 41U, 41V, 41W as the rotor of the rotating electric machine 40 rotates and is applied to the battery pack 20 and the smoothing capacitor 32. In the present embodiment, as the three-phase short-circuit control, the control device 70 performs a control in which each upper arm switch QUH to QWH is turned off and each lower arm switch QUL to QWL is turned on.

[0053] Below, use Figure 3The structure of the control device 70 related to the implementation of three-phase short-circuit control is described. The control device 70 includes an input circuit 71 and a power circuit 72. The input circuit 71 and the power circuit 72 are arranged in a low-voltage area. The positive terminal of the low-voltage power supply 26 is connected to the input circuit 71 via the fuse 25. The grounding piece as the grounding part is connected to the negative terminal of the low-voltage power supply 26. The low-voltage power supply 26 is a secondary battery whose output voltage (rated voltage) is lower than the output voltage (rated voltage) of the battery pack 20 (for example, 12V), for example, a lead storage battery. The power circuit 72 is powered by the input circuit 71 and generates a second voltage V2. In the present embodiment, the power circuit 72 generates a second voltage V2 (for example, 5V) by stepping down the first voltage V1 output by the input circuit 71.

[0054] The control device 70 has a microcomputer 73. The microcomputer 73 includes a CPU and peripheral circuits thereof. The peripheral circuits include an input / output unit for exchanging signals with the outside. The detection values ​​of the monitoring unit 50, the acceleration sensor 52, the phase current sensor 62, the neutral point current sensor 63 and the angle sensor 64, the signal notifying the on / off of the start switch 51 and the signal Sge indicating the leakage detection action of the detection unit 53d are input to the microcomputer 73. The microcomputer 73 generates a switching instruction for alternately turning on the upper arm switches QUH~QWH of each phase and the lower arm switches QUL~QWL of each phase by performing the above-mentioned PWM processing. In addition, the input circuit 71, the power supply circuit 72 and the microcomputer 73 are arranged in the low-voltage area of ​​the control device 70.

[0055] The control device 70 includes an insulating power supply 74, an upper arm driver 75, and a lower arm driver 76. The insulating power supply 74 and the drivers 75 and 76 are arranged in the low-voltage area and the high-voltage area across the boundary between the low-voltage area and the high-voltage area electrically insulated from the low-voltage area in the control device 70. For example, the insulating power supply 74 includes an upper arm insulating power supply that is individually provided for the upper arm drivers 75 of the three phases and a lower arm insulating power supply that is common to the lower arm drivers 76 of the three phases. In addition, the lower arm insulating power supply may also be individually provided for the lower arm drivers 76 of the three phases.

[0056] The isolated power supply 74 generates an upper arm drive voltage VdH supplied to the upper arm driver 75 and a lower arm drive voltage VdL supplied to the lower arm driver 76 based on the first voltage V1 supplied from the input circuit 71, and outputs them to the high voltage region. The isolated power supply 74 is, for example, a flyback type isolated power supply.

[0057] The upper arm driver 75 is individually provided corresponding to each phase upper arm switch QUH~QWH. The upper arm driver 75 has an upper arm driving unit and an upper arm insulation transmission unit. The upper arm driving unit is provided in the high voltage region. The upper arm insulation transmission unit is provided in the low voltage region and the high voltage region across the boundary between the low voltage region and the high voltage region. The upper arm insulation transmission unit transmits the switch command output from the microcomputer 73 to the upper arm driving unit while electrically insulating the low voltage region from the high voltage region. The upper arm insulation transmission unit is, for example, a photocoupler or a magnetic coupler.

[0058] The upper arm driving section and the upper arm insulation transmission section of the upper arm driver 75 are configured to be operable by the upper arm driving voltage VdH supplied by the insulation power supply 74. The upper arm insulation transmission section of the upper arm driver 75 is configured to be operable by the second voltage V2 supplied by the power supply circuit 72.

[0059] When the switch command of each upper arm switch QUH~QWH inputted via the upper arm insulation transmission part is a turn-on command, the upper arm driving part supplies a charging current to the gate of each upper arm switch QUH~QWH. As a result, the gate voltage of each upper arm switch QUH~QWH becomes greater than the threshold voltage Vth, and each upper arm switch QUH~QWH is turned on. On the other hand, when the switch command of each upper arm switch QUH~QWH inputted by the upper arm driving part is a turn-off command, a discharge current flows from the gate of each upper arm switch QUH~QWH to the emitter side. As a result, the gate voltage of each upper arm switch QUH~QWH is less than the threshold voltage Vth, and each upper arm switch QUH~QWH is turned off.

[0060] Each upper arm switch QUH~QWH includes each upper arm sensing terminal SUH~SWH. A small current having a correlation with the collector current of the corresponding upper arm switch QUH~QWH flows through each upper arm sensing terminal SUH~SWH. The current flowing through each upper arm sensing terminal SUH~SWH is detected as a potential difference (hereinafter referred to as an upper arm sensing voltage) of the upper arm sensing resistor RUH~RWH connected to the sensing terminal SUH~SWH, and is input to the upper arm driver 75. The detection value of the upper arm sensing voltage is input to the microcomputer 73 via the upper arm driver 75.

[0061] The lower arm driver 76 is individually provided corresponding to the lower arm switches QUL to QWL of each phase. The lower arm driver 76 has a lower arm driving unit and a lower arm insulation transmission unit. The lower arm driving unit is provided in the high voltage region. The lower arm insulation transmission unit is provided in the low voltage region and the high voltage region across the boundary between the low voltage region and the high voltage region. The lower arm insulation transmission unit transmits the switch command output from the microcomputer 73 to the lower arm driving unit while electrically insulating the low voltage region from the high voltage region. The lower arm insulation transmission unit is, for example, a photocoupler or a magnetic coupler.

[0062] The structures of the lower arm driving section and the lower arm insulation transmission section in the lower arm driver 76 on the high voltage region side are configured to be operable by the lower arm driving voltage VdL supplied by the insulation power supply 74. The structures of the lower arm insulation transmission section in the lower arm driver 76 on the low voltage region side are configured to be operable by the second voltage V2 supplied by the power supply circuit 72.

[0063] When the switch command of each lower arm switch QUL~QWL inputted via the lower arm insulation transmission part is a turn-on command, the lower arm driving part supplies a charging current to the gate of each lower arm switch QUL~QWL. As a result, the gate voltage of each lower arm switch QUL~QWL becomes greater than the threshold voltage Vth, and each lower arm switch QUL~QWL is turned on. On the other hand, when the switch command of each lower arm switch QUL~QWL inputted by the lower arm driving part is a turn-off command, a discharge current flows from the gate of each lower arm switch QUL~QWL to the emitter side. As a result, the gate voltage of each lower arm switch QUL~QWL is less than the threshold voltage Vth, and each lower arm switch QUL~QWL is turned off.

[0064] Each lower arm switch QUL~QWL includes each lower arm sensing terminal SUL~SWL. A small current having a correlation with the collector current of the corresponding lower arm switch QUL~QWL flows through each lower arm sensing terminal SUL~SWL. The current flowing through each lower arm sensing terminal SUL~SWL is detected as a potential difference (hereinafter referred to as a lower arm sensing voltage) of the lower arm sensing resistor RUL~RWL connected to the sensing terminal SUL~SWL, and is input to the lower arm driver 76. The detection value of the lower arm sensing voltage is input to the microcomputer 73 via the lower arm driver 76.

[0065] The control device 70 includes a signal transmission unit 77 and a determination unit 81. The signal transmission unit 77 is arranged in the low-voltage area and the high-voltage area across the boundary between the low-voltage area and the high-voltage area. The signal transmission unit 77 transmits the short-circuit request signal Sg1 output from the microcomputer 73 to the determination unit 81 while electrically insulating the low-voltage area from the high-voltage area. Here, the short-circuit request signal Sg1 is a signal indicating whether there is an execution request for three-phase short-circuit control. Specifically, when the logic of the short-circuit request signal Sg1 is L, it indicates that there is no execution request for three-phase short-circuit control, and when the logic of the short-circuit request signal Sg1 is H, it indicates that there is an execution request for three-phase short-circuit control.

[0066] The microcomputer 73 determines whether there is a request for executing the three-phase short-circuit control. Specifically, the microcomputer 73 determines that there is a request for executing the three-phase short-circuit control in at least one of the following cases: when it is determined that an abnormality has occurred in the power conversion system 10, when it is determined that the vehicle is being towed, and when a signal Sge indicating that a leakage detection action is being performed is obtained. When the microcomputer 73 determines that there is a request for executing the three-phase short-circuit control, the microcomputer 73 outputs a short-circuit request signal Sg1 of logic H. On the other hand, when it is determined that there is no request for executing the three-phase short-circuit control, the microcomputer 73 outputs a short-circuit request signal Sg1 of logic L. In the present embodiment, the microcomputer 73 is equivalent to a "determination unit".

[0067] In addition, the reason why it is determined that there is a request for executing the three-phase short-circuit control during the traction of the vehicle is that the rotor of the rotating electric machine 40 is rotated by the traction of the vehicle, and the back electromotive force generated in each phase winding 41U, 41V, and 41W may become higher. The reason why it is determined that there is a request for executing the three-phase short-circuit control when performing the leakage detection action is to appropriately perform the leakage detection action. In detail, since each lower arm switch QUL~QWL is turned on by implementing the three-phase short-circuit control, the leakage detection device 53 is electrically connected to the rotating electric machine 40. In this case, in the leakage detection action, it can be detected that leakage has occurred in the structure closer to the rotating electric machine 40 side than the inverter 30.

[0068] The abnormality of the power conversion system 10 includes an abnormality of the power conversion device 11, an abnormality of the battery pack 20, and a circuit-breaking fault of each disconnecting switch 23, 24. For example, when the microcomputer 73 determines that each disconnecting switch 23, 24 is open while the start switch 51 is turned on, it can be determined that a circuit-breaking fault of each disconnecting switch 23, 24 has occurred.

[0069] The abnormality of the battery pack 20 includes an overvoltage abnormality or a low voltage abnormality in at least one of the battery pack 20, the first storage battery 21, and the second storage battery 22. The microcomputer 73 may determine whether the abnormality of the battery pack 20 has occurred based on the detection value of the monitoring unit 50.

[0070] Specifically, when the microcomputer 73 determines that the terminal voltage VB of the battery pack 20 exceeds the upper limit voltage of the operating voltage range of the battery pack 20, it is sufficient to determine that an overvoltage abnormality has occurred in the battery pack 20. On the other hand, when the microcomputer 73 determines that the terminal voltage VB of the battery pack 20 is lower than the lower limit voltage of the operating voltage range of the battery pack 20, it is sufficient to determine that a low voltage abnormality has occurred in the battery pack 20. When the microcomputer 73 determines that the terminal voltage VH of the first storage battery 21 exceeds the upper limit voltage of the operating voltage range of the first storage battery 21, it is sufficient to determine that an overvoltage abnormality has occurred in the first storage battery 21. On the other hand, when the microcomputer 73 determines that the terminal voltage VH of the first storage battery 21 is lower than the lower limit voltage of the operating voltage range of the first storage battery 21, it is sufficient to determine that a low voltage abnormality has occurred in the first storage battery 21. When the microcomputer 73 determines that the terminal voltage VL of the second storage battery 22 exceeds the upper limit voltage of the operating voltage range of the second storage battery 22, it is sufficient to determine that an overvoltage abnormality has occurred in the second storage battery 22. On the other hand, when the microcomputer 73 determines that the terminal voltage VL of the second storage battery 22 is lower than the lower limit voltage of the operating voltage range of the second storage battery 22 , it is sufficient to determine that a low voltage abnormality has occurred in the second storage battery 22 .

[0071] The abnormality of the power conversion device 11 includes an abnormality of the inverter 30, an abnormality of the rotating electrical machine 40, and an abnormality of the control device 70. The abnormality of the rotating electrical machine 40 includes an abnormality of the acceleration and deceleration of the vehicle that has unexpectedly occurred. The microcomputer 73 may determine whether the acceleration and deceleration of the vehicle that has unexpectedly occurred based on the detection value of at least one of the acceleration sensor 52 and the angle sensor 64.

[0072] The abnormality of the inverter 30 includes a short circuit fault. A short circuit fault is a fault in which at least one of the switches QUH to QWL remains on. The microcomputer 73 may determine whether a short circuit fault has occurred based on at least one of the detection values ​​of the phase currents Iu, Iv, Iw, the upper arm sense voltage, and the lower arm sense voltage.

[0073] The abnormality of the control device 70 includes an abnormality that power cannot be supplied from the low-voltage power supply 26 to the control device 70 and an abnormality in the control device 70. The abnormality in the control device 70 includes an abnormality in the input circuit 71, an abnormality in the power circuit 72, an abnormality that the switch command cannot be normally transmitted from the microcomputer 73 to the upper arm driver 75 and the lower arm driver 76, and an abnormality that the voltage cannot be output from the insulating power supply 74. The abnormality that the voltage cannot be output from the insulating power supply 74 includes an abnormality of the insulating power supply 74 and an abnormality that power cannot be supplied from the low-voltage power supply 26 to the insulating power supply 74. Here, the abnormality that power cannot be supplied from the low-voltage power supply 26 to the insulating power supply 74 occurs, for example, due to a disconnection of the electrical path from the low-voltage power supply 26 to the insulating power supply 74. In addition, taking the lower arm driver 76 as an example, the abnormality that the switch command cannot be normally transmitted includes an abnormality that the signal path from the microcomputer 73 to the lower arm insulating transmission part is disconnected.

[0074] The abnormality of the power conversion system 10 is caused by, for example, a collision of a vehicle. The microcomputer 73 may also determine whether a collision of the vehicle has occurred based on the detection value of the acceleration sensor 52. The microcomputer 73 may also determine that there is a request for executing the three-phase short-circuit control when it is determined that a collision of the vehicle has occurred. In addition, the microcomputer 73 may determine that there is a request for executing the three-phase short-circuit control when it is determined that at least one of the abnormalities of the power conversion system 10 has occurred.

[0075] The control device 70 includes an abnormal power supply 80 in its high voltage region. The abnormal power supply 80 generates an abnormal drive voltage by supplying the output voltage of the smoothing capacitor 32. The abnormal power supply 80 is, for example, a switching power supply or a series power supply.

[0076] The control device 70 includes a normal power supply path 82, a normal diode 83, an abnormal power supply path 84, and an abnormal switch 85 in its high voltage region. The normal power supply path 82 connects the output side of the isolated power supply 74 to the lower arm driver 76, and supplies the lower arm drive voltage VdL to the lower arm driver 76. The normal diode 83 is provided at a middle position of the normal power supply path 82 in a state where the anode is connected to the output side of the isolated power supply 74.

[0077] The portion of the normal power supply path 82 closer to the lower arm driver 76 than the normal diode 83 is connected to the abnormal power supply 80 via an abnormal power supply path 84. The abnormal switch 85 is provided in the abnormal power supply path 84. The abnormal power supply path 84 supplies the lower arm driver 76 with an abnormal drive voltage.

[0078] The short-circuit request signal Sg1 is input to the determination unit 81 via the signal transmission unit 77. In addition, the lower arm drive voltage VdL of the insulating power supply 74 is supplied to the determination unit 81. The determination unit 81 determines that the three-phase short-circuit control is performed when at least one of the conditions that the short-circuit request signal Sg1 of logic H is input and the condition that the lower arm drive voltage VdL is lower than the specified voltage Vp is satisfied. Here, in order to suppress the occurrence of upper and lower arm short circuits when the three-phase short-circuit control is performed, the specified voltage Vp can be set to a value that can be determined to have passed a sufficient period until each upper arm switch QUH~QWH is disconnected. The specified voltage Vp can be set to, for example, the same value as the above-mentioned threshold voltage Vth or a value less than the threshold voltage Vth. When the determination unit 81 determines that the three-phase short-circuit control is performed, the abnormal switch 85 is switched on. Thus, power is supplied to the lower arm driver 76. In addition, the determination unit 81 outputs the on command of each lower arm switch QUL~QWL to the lower arm driver 76. Thus, the three-phase short-circuit control is performed.

[0079] In addition, when the connection switch 61a is turned on, it is sometimes determined that there is a request to execute the three-phase short-circuit control. Specifically, during the execution of the temperature increase control or the temperature increase motor drive control, it is sometimes determined that there is a request to execute the three-phase short-circuit control. In this case, due to the three-phase short-circuit control, the back electromotive force generated in each phase winding 41U, 41V, 41W may be applied to the battery pack 20 via the connection path 60. Therefore, the reliability of the battery pack 20 may be reduced.

[0080] Unlike this embodiment, Figure 4 and Figure 5 A comparative example is shown in which the three-phase short-circuit control is performed in which the lower arm switches QUL to QWL are turned on while the connection switch 61 a is turned on. Figure 4 1 is a diagram showing the changes of the currents Iu, Iv, and Iw of each phase before and after the three-phase short-circuit control is performed. Figure 5 FIG. 1 is a diagram showing an example of a current path formed during execution of three-phase short-circuit control. Figure 4 After time t1, with the connection switch 61a turned on, three-phase short-circuit control is performed.

[0081] In this case, for example Figure 5 As shown, a current path including the second battery 22, the connection path 60, the V-phase winding 41V, and the V-phase lower arm switch QVL is formed. In this state, the neutral point O and the intermediate terminal B are short-circuited, and power is continuously supplied from the second battery 22 to the rotating electric machine 40. Therefore, the DC component of each phase current Iu, Iv, and Iw increases. As a result, the voltage applied to the second battery 22 increases, and an overvoltage abnormality of the second battery 22 may occur.

[0082] In addition, even when temperature rise control or temperature rise motor drive control is performed, the above-mentioned current path can be formed by turning on the V-phase lower arm switch QVL. However, when temperature rise control or temperature rise motor drive control is performed, unlike the case of three-phase short-circuit control, since the lower arm switches QUL, QVL, and QWL are not turned on at the same time, it is possible to suppress a large current from flowing through the connection path 60.

[0083] In the present embodiment, the power conversion device 11 has a configuration that suppresses a large current from flowing through the connection path 60 when the three-phase short-circuit control is performed while the connection switch 61 a is turned on.

[0084] The microcomputer 73 disconnects the connection switch 61a when it is determined that there is an execution request for three-phase short-circuit control. Specifically, the control device 70 includes a drive circuit 86 in its high-voltage region. The drive circuit 86 is a circuit for switching the connection switch 61a on and off. The short-circuit request signal Sg1 output from the microcomputer 73 is input to the drive circuit 86 via the signal transmission unit 77. When the short-circuit request signal Sg1 of logic H is input, the drive circuit 86 switches the connection switch 61a to be disconnected. In addition, when the short-circuit request signal Sg1 of logic L is input, the drive circuit 86 maintains the connection and disconnection of the connection switch 61a as the current state. In addition, the drive voltage of the insulating power supply 74 can be supplied to the drive circuit 86, and the abnormal drive voltage can also be supplied. In the present embodiment, the drive circuit 86 is equivalent to a "cut-off unit".

[0085] Figure 6 The following is a processing procedure of the microcomputer 73 for controlling the interruption of the current flowing through the connection path 60. This control is repeatedly performed by the microcomputer 73 at a predetermined control cycle, for example.

[0086] In step S30, it is determined whether there is a request to execute the three-phase short-circuit control. If a negative determination is made in step S30, the present process is terminated. On the other hand, if an affirmative determination is made in step S30, the process proceeds to step S31.

[0087] In step S31, the logic of the short-circuit request signal Sg1 is switched to H. Thus, the short-circuit request signal Sg1 of logic H is input to the drive circuit 86, and the connection switch 61a is turned off. As a result, the current flowing in the connection path 60 is cut off.

[0088] Figure 7 and Figure 8 An example of control when three-phase short-circuit control is performed in a state where the connection switch 61a is turned on is shown. Figure 7 1 is a diagram showing the changes of the currents Iu, Iv, and Iw of each phase before and after the three-phase short-circuit control is performed. Figure 8FIG. 1 is a diagram showing an example of a current path formed during execution of three-phase short-circuit control. Figure 7 After time t1, the connection switch 61a is opened, and three-phase short-circuit control is performed.

[0089] In this case, for example Figure 8 As shown, a current path including the V-phase winding 41V, the V-phase lower arm switch QVL, the W-phase lower arm switch QWL, and the W-phase winding 41W is formed. In this state, power is consumed by the current flowing back between the rotating motor 40 and the inverter 30. As a result, the amplitude of each phase current Iu, Iv, and Iw is reduced. In addition, by disconnecting the connection switch 61a, the battery pack 20 is not electrically connected to the rotating motor 40, so that the voltage applied to the battery pack 20 can be suppressed.

[0090] According to the present embodiment, when the microcomputer 73 determines that there is a request to execute the three-phase short-circuit control, the connection switch 61a is turned off. As a result, during the period of the three-phase short-circuit control, the connection switch 61a can be prevented from being turned on. Therefore, during the period of the three-phase short-circuit control, the rotating electric machine 40 and the battery pack 20 can be prevented from being short-circuited via the connection path 60, and a voltage can be applied to the first battery 21 and the second battery 22. As a result, the first battery 21 and the second battery 22 can be prevented from becoming an overvoltage state, and the reliability of the first battery 21 and the second battery 22 can be prevented from being reduced.

[0091] When a signal Sge indicating that a leakage detection action is to be performed is obtained, it is determined that there is a request for execution of three-phase short-circuit control. In this case, the connection switch 61a is disconnected, and the leakage detection action of the high voltage circuit is performed in the state of performing three-phase short-circuit control. In the leakage detection action of the high voltage circuit, it is possible to detect that leakage has occurred in a structure closer to the rotating electrical machine 40 side than the inverter 30. Therefore, compared with the case where the leakage detection action is performed in a state where each switch QUH~QWL is disconnected, a wide range of structures can be used as the object of leakage detection. In addition, during the period of performing three-phase short-circuit control, since the connection switch 61a is disconnected, it is possible to suppress the reduction in the reliability of the first battery 21 and the second battery 22 as described above. That is, according to the present embodiment, it is possible to appropriately perform the leakage detection action while suppressing the reduction in the reliability of the first battery 21 and the second battery 22.

[0092] <Second embodiment> The second embodiment is described below with the differences from the first embodiment as the center. In this embodiment, the structure of the connection switch is changed. Here, the structure of the connection switch that shortens the period of three-phase short-circuit control when the connection switch is turned on is described.

[0093] like Fig. 9 As shown in FIG. 1 , the power conversion device 11 includes a connection switch 61 b ​​instead of the connection switch 61 a in the first embodiment. Fig. 9 For the sake of convenience, Figure 1 The same structures are denoted by the same symbols.

[0094] The connection switch 61b of this embodiment is a switch that switches the conduction and disconnection of the current flowing in the connection path 60, and is a connection switch with a shorter turn-off time than the connection switch 61a of the first embodiment and a higher on-resistance than the connection switch 61a of the first embodiment. For example, the connection switch 61b is a semiconductor switch element that conducts and disconnects a bidirectional current, and specifically, is composed of a pair of IGBTs. The connection switch 61b is switched on and off by the drive circuit 86 in the same manner as the connection switch 61a of the first embodiment.

[0095] When the connection switch 61b is used, the current flowing in the connection path 60 is cut off at a higher speed than when the connection switch 61a of the first embodiment is used, but the surge voltage generated by the current cutoff may increase. Therefore, since a high voltage is applied to the connection switch 61b, the reliability of the connection switch 61b may be reduced.

[0096] Therefore, the power conversion device 11 includes a first diode 91, a second diode 92, and a parallel capacitor 93. The anode of the first diode 91 is connected between the connection switch 61b and the neutral point O, and the cathode of the first diode 91 is connected to the positive side bus Lp. The anode of the second diode 92 is connected between the connection switch 61b and the intermediate terminal B, and the cathode of the second diode 92 is connected to the positive side bus Lp. The parallel capacitor 93 is provided in the connection path 60 and is connected in parallel with the connection switch 61b.

[0097] Fig.10 An example of control before and after three-phase short-circuit control is shown. Fig.10 In FIG. 1 , (a) shows the control state of the power conversion device 11, (b) shows the change of the terminal voltage VB of the battery pack 20, and (c) shows the change of each phase current Iu, Iv, and Iw. Fig.10 In (b), the solid line shows the change of the terminal voltage VB of the battery pack 20 in this embodiment, and the dotted line shows the change of the terminal voltage VBref of the battery pack 20 in the comparative example using a connection switch having a longer off period than the connection switch 61b.

[0098] exist Fig.10Before time t1, either the temperature rise control or the temperature rise motor drive control is performed. That is, before time t1, the connection switch 61b is turned on. At time t1, the microcomputer 73 determines that the terminal voltage VB of the battery pack 20 exceeds the upper limit voltage Vα, performs three-phase short-circuit control, and the connection switch 61b is turned off. In addition, the upper limit voltage Vα is, for example, the upper limit voltage of the operating voltage range of the battery pack 20.

[0099] After time t1, the connection switch 61b is quickly opened. As a result, since the battery pack 20 and the rotating electric machine 40 are electrically disconnected, it is possible to suppress the voltage applied to the battery pack 20 due to the connection between the battery pack 20 and the rotating electric machine 40 via the connection path 60 during the execution of the three-phase short-circuit control. Therefore, for example, the terminal voltage VB of the battery pack 20 gradually decreases to the terminal voltage Vβ during the charging and discharging stop. In this case, compared with the case where a connection switch with a longer shutdown period than the connection switch 61b is used, the increase of the terminal voltage VB of the battery pack 20 can be reliably suppressed. In addition, in the case of using a connection switch with a longer shutdown period than the connection switch 61b, the period during which the battery pack 20 and the rotating electric machine 40 are connected via the connection path 60 becomes longer than the case of using the connection switch 61b. Therefore, the terminal voltage VBref of the battery pack 20 of the comparative example increases compared with the terminal voltage VB of the battery pack 20 of the present embodiment.

[0100] At time t1, three-phase short-circuit control is performed, and a surge voltage is generated as the connection switch 61b is disconnected. Fig.10 As shown in (c), transient currents Pu, Pv, and Pw are superimposed on each phase current Iu, Iv, and Iw. In this embodiment, the first diode 91 and the second diode 92 can ensure a path for the transient currents Pu, Pv, and Pw to flow back. In addition, the parallel capacitor 93 can suppress the voltage change caused by the transient currents Pu, Pv, and Pw.

[0101] According to the present embodiment described in detail above, the following effects can be obtained.

[0102] In the present embodiment, a connection switch 61b is provided in the connection path 60. In this case, the period from when it is determined that there is a request for execution of the three-phase short-circuit control to when the connection switch 61b is turned off is shorter than the case where a switch having a longer off period than the connection switch 61b is provided. Thus, when the connection switch 61b is turned on, the period during which the three-phase short-circuit control is performed is shorter than the case where a switch having a longer off period than the connection switch 61b is provided. Therefore, it is possible to reliably suppress the rise in the terminal voltage VB of the battery pack 20.

[0103] The three-phase short-circuit control is performed, and a surge voltage is generated as the connection switch 61b is disconnected. Due to the generation of the surge voltage, transient currents Pu, Pv, and Pw are superimposed on the currents Iu, Iv, and Iw of each phase, and the voltage applied to the connection switch 61b may increase. As a result, the reliability of the connection switch 61b may be reduced.

[0104] In view of this, the current flowing in the connection path 60 flows back through the first diode 91 and the second diode 92. Thus, the voltage applied to the connection switch 61b due to the generation of transient currents Pu, Pv, and Pw can be suppressed from increasing. In addition, the parallel capacitor 93 is connected in parallel with the connection switch 61b. Thus, the voltage change applied to the connection switch 61b due to the generation of transient currents Pu, Pv, and Pw can be suppressed. Therefore, while performing three-phase short-circuit control, the voltage applied to the connection switch 61b when the connection switch 61b is disconnected can be suppressed. As a result, the occurrence of a situation in which the reliability of the connection switch 61b is reduced can be suppressed.

[0105] Diodes are provided on both sides of the connection switch 61b. Thus, when the connection switch 61b is turned off, when the current flows in the direction from the neutral point O toward the intermediate terminal B, the current flowing in the connection path 60 flows back through the first diode 91. In addition, when the connection switch 61b is turned off, when the current flows in the direction from the intermediate terminal B toward the neutral point O, the current flowing in the connection path 60 flows back through the second diode 92. That is, regardless of whether the direction of the current flowing in the connection path 60 is the direction from the neutral point O toward the intermediate terminal B or the direction from the intermediate terminal B toward the neutral point O, the current flowing in the connection path 60 flows back through one of the first diode 91 and the second diode 92. Therefore, when the connection switch 61b is turned off, it is possible to reliably suppress the increase in the voltage applied to the connection switch 61b.

[0106] In this embodiment, the temperature rise control is performed in the state where the connection switch 61b is turned on. In this case, since the AC current flows in the connection path 60, the current flows in the connection path 60 in both the direction from the neutral point O toward the intermediate terminal B and the direction from the intermediate terminal B toward the neutral point O. In view of this, the present embodiment in which diodes are provided on both sides of the connection switch 61b is a structure suitable for suppressing the increase of the voltage applied to the connection switch 61b when the connection switch 61b is turned off.

[0107] <Third embodiment> The third embodiment is described below, centering on the differences from the first embodiment and the second embodiment. In this embodiment, the structure of the connection switch is changed. Here, a structure that can achieve both high-speed cutoff of the current flowing in the connection path 60 and reduction of the conduction loss generated during the period when the connection switch is turned on is described.

[0108] Even if the three-phase short-circuit control is performed, it is considered that there is a situation where the back electromotive force generated in each phase winding 41U, 41V, 41W does not increase to a level that causes an overvoltage abnormality in the battery pack 20. In this situation, it is desirable to give priority to reducing the conduction loss generated during the conduction period of the connection switch rather than quickly cutting off the current flowing in the connection path 60.

[0109] Therefore, if Fig.11 As shown, the power conversion device 11 includes a first connection switch 61a and a second connection switch 61b connected in parallel with each other. The first connection switch 61a is the connection switch 61a described in the first embodiment, and the second connection switch 61b is the connection switch 61b described in the second embodiment. The second connection switch 61b is provided in the connection path 60. The first connection switch 61a is connected in parallel with the second connection switch 61b. In addition, Fig.11 For the sake of convenience, Figure 1 and Fig. 9 The same structures are denoted by the same symbols.

[0110] Fig.12 FIG. 2 shows the processing steps of the switch control performed by the control device 70. The processing is repeatedly performed by the control device 70 in a predetermined control cycle, for example. Fig.12 For the sake of convenience, Figure 2 The same structures are denoted by the same symbols.

[0111] After the processing of step S12, the process proceeds to step S40. In step S40, the first connection switch 61a is turned off, and the second connection switch 61b is turned off. As a result, the intermediate terminal B and the neutral point O are electrically disconnected. After the processing of step S40, the present process ends. In addition, after the processing of step S14, the process proceeds to step S41. The processing of step S41 is the same as the processing content of step S40. After the processing of step S41, the process proceeds to step S16.

[0112] After the process of step S18, the process proceeds to step S42. In step S42, the first connection switch 61a is turned on, and the second connection switch 61b is turned off. After the process of step S42, the process proceeds to step S20.

[0113] After step S21, the process proceeds to step S43. In step S43, the first connection switch 61a is turned off, and the second connection switch 61b is turned on. After the process of step S43, the process proceeds to step S23.

[0114] According to the present embodiment described in detail above, the following effects can be obtained.

[0115] The second connection switch 61b is provided in the connection path 60, and the first connection switch 61a is connected in parallel with the second connection switch 61b. Here, as described in the second embodiment, the second connection switch 61b is a connection switch having a shorter off time than the first connection switch 61a and a higher on resistance than the first connection switch 61a. In this case, according to the operating conditions of the power conversion device 11, one of the first connection switch 61a and the second connection switch 61b is turned on, thereby achieving high-speed cutoff of the current flowing in the connection path 60 and reduction of the conduction loss generated during the period when the connection switch is turned on.

[0116] When the rotor of the rotating electric machine 40 is rotating, and a back electromotive force is generated in each phase winding 41U, 41V, 41W and it is determined that there is a request for executing the three-phase short-circuit control, it is desirable to quickly disconnect the connection switch. On the other hand, it is considered that the possibility of the battery pack 20 becoming an overvoltage state is low even if the short-circuit control is performed with the connection switch turned on, when the rotation of the rotor of the rotating electric machine 40 stops. In this case, it is desirable to reduce the conduction loss generated during the period when the connection switch is turned on, compared with the high-speed cutoff of the current flowing in the connection path 60.

[0117] Therefore, it is determined whether there is a drive request to drive the rotor of the rotary electric machine 40 to rotate. When it is determined that there is a drive request, the motor drive control or the temperature rise motor drive control is performed while the first connection switch 61a is turned off and the second connection switch 61b is turned on. In this case, the second connection switch 61b having a shorter off period than the first connection switch 61a is turned on. Thus, when it is determined that the three-phase short-circuit control is to be performed, the second connection switch 61b can be turned off more quickly than when the first connection switch 61a is turned on. As a result, compared with the case where the first connection switch 61a is used, the current flowing in the connection path 60 can be cut off at a high speed.

[0118] On the other hand, when it is determined that there is no drive request for driving the rotor of the rotating electrical machine 40, the first connection switch 61a is turned on and the second connection switch 61b is turned off. In this case, the first connection switch 61a having a lower on-resistance than the second connection switch 61b is turned on, and the temperature rise control is performed. As a result, the conduction loss generated during the period when the first connection switch 61a is turned on can be reduced compared to the case of the second connection switch 61b. In this way, by changing the connection switch that is turned on according to the presence or absence of a drive request for the rotating electrical machine 40, it is possible to achieve high-speed cutting of the current flowing in the connection path 60 and reduction of the conduction loss generated during the period when the connection switch is turned on.

[0119] <Modification of the Third Embodiment> Even when the rotor of the rotary electric machine 40 is rotating, if the rotation speed of the rotor is low, the back electromotive force generated in each phase winding 41U, 41V, 41W is considered to be low. In this case, even if the three-phase short-circuit control is performed with the connection switch turned on, the possibility of the battery pack 20 becoming an overvoltage state is considered to be low.

[0120] Therefore, in the present embodiment, the processing steps of the control executed by the control device 70 are changed. Fig.13 FIG. 2 shows the control processing steps executed by the control device 70. The processing is repeatedly executed by the control device 70 in, for example, a predetermined control cycle. Fig.13 For the sake of convenience, Fig.12 The same structures are denoted by the same symbols.

[0121] After the processing of step S21, proceed to step S44. In step S44, voltage information related to the back electromotive force generated in each phase winding 41U, 41V, 41W is obtained. In the present embodiment, the voltage information is the detection value of the angle sensor 64. In addition, the voltage information is not limited to the detection value of the angle sensor 64, but may also be the detection value of the phase current sensor 62, or may be an estimated value of the back electromotive force generated in each phase winding 41U, 41V, 41W estimated based on at least one of the detection value of the phase current sensor 62 and the detection value of the angle sensor 64. In addition, the processing of step S44 is not limited to after the processing of step S21, for example, it may also be performed after the processing of step S10.

[0122] In step S45, it is determined based on the voltage information whether the back electromotive force generated in each phase winding 41U, 41V, 41W is below the allowable value. In the present embodiment, the rotation speed of the rotating motor 40 is calculated based on the detection value of the angle sensor 64. It is determined whether the calculated rotation speed of the rotating motor 40 is below the allowable rotation speed. The allowable rotation speed is preferably set based on the withstand voltage of at least one of the battery pack 20 and the smoothing capacitor 32. In the case where it is determined that the calculated rotation speed of the rotating motor 40 is below the allowable rotation speed, it is determined that the back electromotive force generated in each phase winding 41U, 41V, 41W is below the allowable value. In the case where a negative determination is made in step S45, the process proceeds to step S43. On the other hand, in the case where an affirmative determination is made in step S45, the process proceeds to step S46.

[0123] In addition, in step S44, when the detection value of the phase current sensor 62 is obtained as voltage information, the effective value of each phase current Iu, Iv, and Iw can also be calculated based on the obtained detection value. At this time, it is also possible to determine whether the calculated effective value of each phase current Iu, Iv, and Iw is below the allowable effective value. In addition, when the estimated value of the back electromotive force generated in each phase winding 41U, 41V, and 41W is obtained as voltage information, it is also possible to determine whether the obtained estimated value is below the allowable back electromotive force. The allowable effective value and the allowable back electromotive force are preferably set based on the withstand voltage of at least one of the battery pack 20 and the smoothing capacitor 32.

[0124] In step S46, the first connection switch 61a is turned on, and the second connection switch 61b is turned off. After the process of step S46, the process proceeds to step S23.

[0125] According to the present embodiment, when it is determined that there is a drive request to drive the rotor of the rotary electric machine 40 to rotate, it is determined whether the back electromotive force generated in each phase winding 41U, 41V, 41W is less than the allowable value. When it is determined that the back electromotive force generated in each phase winding 41U, 41V, 41W is less than the allowable value, the first connection switch 61a is turned on and the second connection switch 61b is turned off. In this case, the first connection switch 61a having an on-resistance lower than that of the second connection switch 61b is turned on. That is, even in a state where the rotor of the rotary electric machine 40 rotates, when it is determined that the possibility of the battery pack 20 becoming an overvoltage state is low, it is possible to prioritize the reduction of the conduction loss of the connection switch over the high-speed cutoff of the current flowing in the connection path 60 and the reduction of the conduction loss generated during the period when the connection switch is turned on.

[0126] <Fourth embodiment> The fourth embodiment will be described below, focusing on the differences from the first embodiment. In the present embodiment, the main body of the cutoff control is changed from the microcomputer 73 to the determination unit 81 . Fig.14 2 shows the structure of the control device 70. Fig.14 For the sake of convenience, Figure 3 The same structures are denoted by the same symbols.

[0127] When the determination unit 81 determines that the short-circuit request signal Sg1 of logic H is input, the logic of the disconnection signal Sgf is switched from L to H. Here, the disconnection signal Sgf is a signal indicating whether there is a request to disconnect the first connection switch 61a. Specifically, when the logic of the disconnection signal Sgf is L, it indicates that there is no request to disconnect the first connection switch 61a, and when the logic of the disconnection signal Sgf is H, it indicates that there is a request to disconnect the first connection switch 61a.

[0128] The cutoff signal Sgf is input to the drive circuit 86 instead of the short-circuit request signal Sg1. When the cutoff signal Sgf of logic H is input, the drive circuit 86 switches the first connection switch 61a to off. When the cutoff signal Sgf of logic L is input, the drive circuit 86 maintains the on / off state of the first connection switch 61a.

[0129] Fig.15 1 shows the procedure of the process executed by the determination unit 81. This process is repeatedly executed by the determination unit 81 at a predetermined control cycle, for example.

[0130] In step S50, it is determined whether to perform three-phase short-circuit control. In the present embodiment, it is determined whether at least one of the conditions that the logic of the short-circuit request signal Sg1 is H and the condition that the lower arm drive voltage VdL is lower than the specified voltage Vp is satisfied. In the case of a negative determination in step S50, the present process is terminated. On the other hand, in the case of a positive determination in step S50, the process proceeds to step S51.

[0131] In step S51, the logic of the cutoff signal Sgf is switched to H. Thus, the cutoff signal Sgf of logic H is input to the drive circuit 86, and the first connection switch 61a is turned off. As a result, the current flowing in the connection path 60 is cut off.

[0132] In step S52, three-phase short-circuit control is performed. Specifically, a turn-on command for each of the lower arm switches QUH to QWH is output to the lower arm driver 76. Thus, three-phase short-circuit control is performed.

[0133] According to the present embodiment, before outputting the on command of each lower arm switch QUH to QWH to the lower arm driver 76, the logic of the cutoff signal Sgf is switched to H. Thus, the timing of the process of turning off the first connection switch 61a can be advanced before the timing of outputting the on command of each lower arm switch QUH to QWH. As a result, the occurrence of a situation in which the three-phase short-circuit control is performed in the state where the first connection switch 61a is turned on can be reliably suppressed.

[0134] <Other embodiments> In addition, each of the above-mentioned embodiments may be implemented with the following modifications.

[0135] In the first embodiment, the switch control performed in the state where the first connection switch 61a is turned on is not limited to the temperature increase control and the temperature increase motor drive control. The control device 70 may also perform energy management control in the state where the first connection switch 61a is turned on. As energy management control, the control device 70 turns on and off each switch QUH to QWL in the state where the first connection switch 61a is turned on, so that a direct current flows between the first storage battery 21 and the second storage battery 22 via the switch device unit 31, each phase winding 41U, 41V, 41W and the connection path 60. Thus, power is transmitted from one of the first storage battery 21 and the second storage battery 22 to the other.

[0136] In the case of energy management control instead of temperature rise control, it is better to change the previous Figure 2 Here, as the energy management control, a case where a balancing control is performed for the purpose of balancing the terminal voltage VH of the first storage battery 21 and the terminal voltage VL of the second storage battery 22 will be described.

[0137] In step S10, instead of determining whether there is a temperature increase request, it is determined whether there is a request for balancing the terminal voltage VH of the first battery 21 and the terminal voltage VL of the second battery 22. Specifically, when it is determined that the absolute value of the difference between the terminal voltage VH of the first battery 21 and the terminal voltage VL of the second battery 22 exceeds a predetermined value, it is determined that there is a request for balancing.

[0138] In step S18, balancing control is performed instead of temperature rise control. In step S20, in the PWM processing of balancing control, it is preferable to calculate the U-phase modulation rate, the V-phase modulation rate, and the W-phase modulation rate based on the terminal voltage VH of the first battery 21 and the terminal voltage VL of the second battery 22. In detail, the determination voltage is calculated by subtracting the terminal voltage VL of the second battery 22 from the terminal voltage VH of the first battery 21. When the calculated determination voltage is a positive value, the neutral point command current is set to a positive value. On the other hand, when the calculated determination voltage is a negative value, the neutral point command current is set to a negative value. When setting the neutral point command current, the larger the absolute value of the determination voltage is, the larger the absolute value of the neutral point command current is set. In addition, the neutral point command current of the present embodiment is a direct current. In addition, the PWM processing after setting the neutral point command current is the same as that of the temperature rise control.

[0139] In step S21, the equalizing motor drive control is performed instead of the temperature increase motor drive control. In the PWM control in step S23, it is preferable to calculate the U-phase modulation rate, the V-phase modulation rate, and the W-phase modulation rate based on the torque command value of the rotating electric machine 40, the terminal voltage VH of the first battery 21, and the terminal voltage VL of the second battery 22. In the equalizing motor drive control, it is preferable to set the neutral point command current as in the case of the equalizing control.

[0140] In the energy management control, energy may be transferred between the first storage battery 21 and the second storage battery 22 without aiming at equalizing the terminal voltage VH of the first storage battery 21 and the terminal voltage VL of the second storage battery 22. As a situation where energy is transferred without aiming at equalization, it is assumed that either the first storage battery 21 or the second storage battery 22 can be connected to a charger provided outside the power conversion system 10. In this situation, it is assumed that power is transferred from the storage battery charged by the charger to the other storage battery of the first storage battery 21 or the second storage battery 22.

[0141] In the above situation, by performing energy management control, the current flows in the connection path 60 in either the direction from the neutral point O toward the intermediate terminal B or the direction from the intermediate terminal B toward the neutral point O. Specifically, by performing energy management control to transfer power from the first storage battery 21 to the second storage battery 22, the current flows in the direction from the neutral point O toward the intermediate terminal B in the connection path 60. In addition, by performing energy management control to transfer power from the second storage battery 22 to the first storage battery 21, the current flows in the direction from the intermediate terminal B toward the neutral point O in the connection path 60.

[0142] In the second embodiment and the third embodiment, the second connection switch 61b may be a semiconductor switch element that conducts and cuts off a unidirectional current instead of a semiconductor switch element that conducts and cuts off a bidirectional current. As described above, as the energy management control, it is assumed that the second connection switch 61b is a semiconductor switch element that conducts and cuts off a unidirectional current.

[0143] For example, when controlling the transmission of power from the first storage battery 21 to the second storage battery 22 as energy management control, it is preferable to use a semiconductor switching element that conducts and cuts off the current flowing in the direction from the neutral point O toward the intermediate terminal B. Fig.16 and Fig.17 , a configuration is shown in which an IGBT that conducts and cuts off a current flowing from the neutral point O toward the intermediate terminal B is used as the second connection switch 61b. In addition, for example, when controlling the transmission of power from the second storage battery 22 to the first storage battery 21 as energy management control, it is preferable to use a semiconductor switch element that conducts and cuts off a current flowing from the intermediate terminal B toward the neutral point O. Fig.18 and Fig.19 , a configuration in which an IGBT that conducts and blocks a current flowing in a direction from the intermediate terminal B toward the neutral point O is used as the second connection switch 61 b ​​is shown.

[0144] In the second embodiment, the second connection switch 61 b ​​may be an N-channel MOSFET instead of the IGBT. Fig. 20 It is shown in the previous Fig. 9 In the structure shown in FIG. 1 , the second connection switch 61 b ​​is an example of a pair of N-channel MOSFETs whose sources are connected to each other. Fig.21 As shown in the previous Fig.11 In the illustrated structure, the second connection switch 61 b ​​may be a pair of N-channel MOSFETs whose sources are connected to each other, instead of the IGBT.

[0145] In the second embodiment, at least one of the first diode 91 and the second diode 92 may not be included. For example, when the power is transferred from the first storage battery 21 to the second storage battery 22 as energy management control, the current flows in the connection path 60 in the direction from the neutral point O toward the intermediate terminal B. In this case, Fig. 22As shown, the second diode 92 may not be included. In addition, for example, when the power is transferred from the second storage battery 22 to the first storage battery 21 as energy management control, the current flows in the direction from the intermediate terminal B toward the neutral point O. In this case, as shown in FIG. Fig.23 As shown, the first diode 91 may not be included.

[0146] According to the present embodiment, depending on the execution mode of energy management control, the diode is omitted from the power converter 11. This can reduce the number of diodes included in the power converter 11 and suppress an increase in the voltage applied to the connection switch 61b.

[0147] In the second embodiment, both the first diode 91 and the second diode 92 may not be included.

[0148] In the second embodiment, the parallel capacitor 93 may not be included.

[0149] The first embodiment and its variant, the second embodiment and its variant, the third embodiment and its variant, and the fourth embodiment may be combined and implemented. For example, in order to combine and implement the second embodiment and the third embodiment, Fig.24 As shown in FIG. 1 , the power conversion device 11 may include a first connection switch 61a, a second connection switch 61b, a first diode 91, a second diode 92, and a parallel capacitor 93. In addition, for example, in order to combine and implement the modified example of the second embodiment with the third embodiment, it is also possible to adopt Fig.25 , Fig.26 and Fig. 27 The structure shown. Fig.25 In FIG. 1 , the power conversion device 11 includes a first connection switch 61 a, a second connection switch 61 b, a second diode 92 and a parallel capacitor 93. Fig.26 In FIG. 1 , the power conversion device 11 includes a first connection switch 61 a, a second connection switch 61 b, a first diode 91 and a parallel capacitor 93. Fig. 27 In the embodiment, the power conversion device 11 includes a first connection switch 61 a , a second connection switch 61 b ​​, a first diode 91 , and a second diode 92 .

[0150] As the three-phase short-circuit control, the control device 70 may perform control to turn on each of the upper arm switches QUH to QWH and turn off each of the lower arm switches QUL to QWL.

[0151] The upper arm switch and the lower arm switch constituting the switch device section 31 are not limited to IGBTs, and may be, for example, N-channel MOSFETs. In this case, the high potential side terminal is the drain, and the low potential side terminal is the source.

[0152] The object on which the power conversion system 10 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 rotary electric machine 40 is a flight power source for the airplane, and when the mobile object is a ship, the rotary electric machine 40 is a navigation power source for the ship. In addition, the object on which the power conversion system 10 is installed is not limited to a mobile object.

[0153] · Hereinafter, characteristic structures extracted from the above-mentioned embodiments will be described. [Structure 1] A power conversion device, the power conversion device (11) comprising: A rotating electric machine (40) having star-connected windings (41U, 41V, 41W); and An inverter (30), the inverter having a series connection of upper arm switches (QUH, QVH, QWH) and lower arm switches (QUL, QVL, QWL), wherein the power conversion device comprises: A connection path (60) electrically connecting the negative electrode side of the first storage battery (21) and the positive electrode side of the second storage battery (22) connected in series to the neutral point of the winding; a connection switch (61a, 61b), the connection switch being arranged in the connection path, and being set to be on to electrically connect the negative electrode side of the first storage battery and the positive electrode side of the second storage battery to the neutral point, and being set to be off to electrically disconnect the negative electrode side of the first storage battery and the positive electrode side of the second storage battery from the neutral point; a control unit (70) for controlling the upper arm switch and the lower arm switch while the connection switch is turned on; a determination unit (73, 81) for determining whether to perform short-circuit control in which either one of the upper arm switch and the lower arm switch is turned on and the other is turned off; and A disconnection unit (86) disconnects the connection switch when it is determined that the short-circuit control is to be performed. [Structure 2] The power conversion device as described in Structure 1, wherein: The connection switch is a first connection switch (61a) and a second connection switch (61b) connected in parallel with each other. The second connection switch has a shorter off time than the first connection switch and a higher on resistance than the first connection switch. [Structure 3] The power conversion device as described in Structure 2, wherein: The control unit determines whether there is a drive request to drive the rotor of the rotating electrical machine to rotate. When it is determined that the driving request is present, the switch control is performed while the second connection switch of the first connection switch and the second connection switch is turned on. When it is determined that there is no driving request, the switch control is performed while the first connection switch of the first connection switch and the second connection switch is turned on. [Structure 4] The power conversion device as described in Structure 3, wherein: The control unit acquires voltage information related to the back electromotive force generated in the winding. When it is determined that the drive request is present, it is determined based on the voltage information whether the back electromotive force generated in the winding is below an allowable value, When it is determined that the back electromotive force generated in the winding is equal to or less than the allowable value, the switch control is performed while the first connection switch of the first connection switch and the second connection switch is turned on. [Structure 5] A power conversion device as described in any one of Structures 1 to 4, wherein: comprising diodes (91, 92), An anode of the diode is electrically connected to one of both sides of the connection switch, and a cathode of the diode is electrically connected to a high potential side terminal of the upper arm switch. [Structure 6] The power conversion device as described in Structure 5, wherein: The diodes are a first diode (91) and a second diode (92), The anode of the first diode is electrically connected between the connection switch and the neutral point, and the cathode of the first diode is electrically connected to the high potential side terminal of the upper arm switch. An anode of the second diode is electrically connected between the connection switch and the negative electrode side of the first battery and the positive electrode side of the second battery, and a cathode of the second diode is electrically connected to a high potential side terminal of the upper arm switch. [Structure 7] The power conversion device as described in Structure 6, wherein: The control unit performs the switch control so that the AC current flows through the connection path while turning on the connection switch. [Structure 8] A power conversion device as described in any one of Structures 1 to 7, wherein: A capacitor (93) is included, and the capacitor is connected in parallel with the connection switch.

[0154] 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 (11) comprising: A rotating electric machine (40) having star-connected windings (41U, 41V, 41W); as well as An inverter (30) comprising a series connection of upper arm switches (QUH, QVH, QWH) and lower arm switches (QUL, QVL, QWL), The power conversion device comprises: A connection path (60) electrically connecting the negative electrode side of a first storage battery (21) and a positive electrode side of a second storage battery (22) connected in series to a neutral point of the winding; a connection switch (61a, 61b), the connection switch being arranged in the connection path, and being set to be on to electrically connect the negative electrode side of the first storage battery and the positive electrode side of the second storage battery to the neutral point, and being set to be off to electrically disconnect the negative electrode side of the first storage battery and the positive electrode side of the second storage battery from the neutral point; a control unit (70) which turns on the connection switch and performs switch control of the upper arm switch and the lower arm switch; a determination unit (73, 81) for determining whether to perform short-circuit control in which either one of the upper arm switch and the lower arm switch is turned on and the other is turned off; and A disconnection unit (86) disconnects the connection switch when it is determined that the short-circuit control is to be performed.

2. The power conversion device according to claim 1, characterized in that: The connection switches are a first connection switch (61a) and a second connection switch (61b) connected in parallel to each other, The second connection switch has a shorter turn-off time than the first connection switch and a higher on-resistance than the first connection switch.

3. The power conversion device according to claim 2, characterized in that: The control unit determines whether there is a drive request to drive the rotor of the rotating electrical machine to rotate. When it is determined that the drive request exists, the second connection switch of the first connection switch and the second connection switch is turned on and the switch control is performed, When it is determined that there is no driving request, the first connection switch of the first connection switch and the second connection switch is turned on, and the switch control is performed.

4. The power conversion device according to claim 3, characterized in that: The control unit acquires voltage information related to the back electromotive force generated in the winding, When it is determined that the drive request is present, determining whether the back electromotive force generated in the winding is below a permissible value based on the voltage information, When it is determined that the back electromotive force generated in the winding is equal to or less than the allowable value, the first connection switch of the first connection switch and the second connection switch is turned on, and the switch control is performed.

5. The power conversion device according to claim 1, characterized in that: comprising diodes (91, 92), An anode of the diode is electrically connected to one of both sides of the connection switch, and a cathode of the diode is electrically connected to a high potential side terminal of the upper arm switch.

6. The power conversion device according to claim 5, characterized in that: The diodes are a first diode (91) and a second diode (92), The anode of the first diode is electrically connected between the connection switch and the neutral point, and the cathode of the first diode is electrically connected to the high potential side terminal of the upper arm switch. An anode of the second diode is electrically connected between the connection switch and the negative electrode side of the first battery and the positive electrode side of the second battery, and a cathode of the second diode is electrically connected to a high potential side terminal of the upper arm switch.

7. The power conversion device according to claim 6, characterized in that: The control unit turns on the connection switch and performs the switch control so that an alternating current flows in the connection path.

8. The power conversion device according to claim 1, wherein: A capacitor (93) is included and the capacitor is connected in parallel with the connection switch.

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