Electric vehicle heat management method and electric vehicle heat management system

Abstract

Provided is a heat management method for an electric vehicle comprising an exhaust heat circulation path for taking in exhaust heat from an inverter that transfers and receives electric power to / from a traveling motor which drives the electric vehicle, wherein a drive voltage for driving a switching element that constitutes the inverter is applied to a gate terminal of the switching element via a variable resistance part, and a resistance value of the variable resistance part when the exhaust heat stored in the exhaust heat circulation path is supplied to the outside is set higher than a resistance value of the variable resistance part before the exhaust heat is supplied to the outside.

Description

Thermal management method for electric vehicle and thermal management system for electric vehicle

[0001] The present invention relates to a thermal management method for an electric vehicle and a thermal management system for an electric vehicle.

[0002] JP6131715B discloses a technology for warming up the rotor of a traction motor that drives an electric vehicle by periodically passing a d-axis current through the rotor when the motor is stopped, thereby generating eddy currents in the core of the coil of the motor.

[0003] In relation to JP6131715B, a technology has been proposed for an electric vehicle equipped with an exhaust heat circulation path that takes in exhaust heat from an inverter that exchanges power with a traction motor, and supplies the exhaust heat to other systems within the electric vehicle. However, it is difficult to obtain sufficient exhaust heat from the inverter during normal control such as when the electric vehicle is running.

[0004] Therefore, the present invention aims to provide a thermal management method and a thermal management system for an electric vehicle that is equipped with a waste heat circulation path that takes in waste heat from an inverter that exchanges power with a driving motor, and that can efficiently extract waste heat from the inverter when supplying the waste heat to the outside of the waste heat circulation path.

[0005] According to one aspect of the present invention, there is provided a thermal management method for an electric vehicle having an exhaust heat circulation path that takes in exhaust heat from an inverter that exchanges power with a traction motor that drives the electric vehicle. In this method, a drive voltage that drives a switching element constituting the inverter is applied to a gate terminal of the switching element via a variable resistor. Then, the resistance value of the variable resistor when supplying the exhaust heat stored in the exhaust heat circulation path to the outside is set higher than the resistance value of the variable resistor before supplying the exhaust heat to the outside.

[0006] FIG. 1 is a schematic diagram of a thermal management system according to this embodiment. FIG. 2 is a diagram showing the flow path of the heat medium during normal operation. FIG. 3 is a diagram showing the flow path of the heat medium during battery heating. FIG. 4 is a circuit diagram of the powertrain. FIG. 5 is a circuit diagram of the variable resistor unit. FIG. 6 is a time chart showing the first drive voltage, the on / off state of the first switching element, the second drive voltage, and the on / off state of the second switching element when the ePT heat recovery flag is in the off state. FIG. 7 is a time chart showing the first drive voltage, the on / off state of the first switching element, the second drive voltage, and the on / off state of the second switching element when the ePT heat recovery flag is in the on state. FIG. 8 is a flow chart showing the process of starting battery warm-up in the thermal management system according to this embodiment. FIG. 9 is a flow chart showing the process of stopping battery warm-up in the thermal management system according to this embodiment. FIG. 10 is a diagram showing the relationship between the temperature of the variable resistor unit and the dead time. FIG. 11 is a diagram showing a modified example of the variable resistor unit.

[0007] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0008] 1 is a schematic diagram of a thermal management system TM according to this embodiment. The thermal management system TM is installed in, for example, an electric vehicle. Note that the electric vehicle referred to here includes not only a battery electric vehicle (BEV) but also a hybrid electric vehicle (HEV).

[0009] The thermal management system TM comprises an air conditioning device 3 including a first heat exchange circuit 1 (exhaust heat circulation path), a second heat exchange circuit 2, a third heat exchange circuit 31 that exchanges heat with the first heat exchange circuit 1, a connecting mechanism 4 that connects the first heat exchange circuit 1 and the second heat exchange circuit 2, and a controller 100.

[0010] The first heat exchange circuit 1 is arranged with a first pump 11, a battery 12, a chiller 35, and a first tank 14, and is arranged so that a heat medium (water or coolant liquid) circulates in this order.

[0011] The chiller 35 is incorporated in the third heat exchange circuit 31 of the air conditioning unit 3, and performs heat exchange between the heat medium circulating through the first heat exchange circuit 1 and the heat medium circulating through the third heat exchange circuit 31 (e.g., an alternative refrigerant such as HFC134a).

[0012] The first pump 11 pumps the heat medium stored in the first tank 14 toward the battery 12 .

[0013] The battery 12 supplies power to an inverter 25 of a traction motor 26 that drives the electric vehicle. The battery 12 generates heat during charging and discharging, and supplies heat to the heat medium.

[0014] A battery temperature sensor 13 is disposed downstream of the battery 12 in the first heat exchange circuit 1 , and outputs information on the temperature of the heat medium discharged from the battery 12 to the controller 100 .

[0015] The first tank 14 stores the heat medium discharged from the chiller 35 .

[0016] A third heat exchange circuit 31 constituting the air conditioner 3 includes a chiller 35, a compressor 32, a condenser 33, an expander 34, and another chiller 35, which are arranged in this order so that the heat medium circulates.

[0017] The compressor 32 compresses the heat medium discharged from the chiller 35 to produce a high-temperature, high-pressure gas, and supplies the gas to the condenser 33 .

[0018] The condenser 33 is disposed in a position inside a duct 37 for interior air conditioning of the electric vehicle where it is exposed to the air from the interior of the vehicle sent from the blower 36. The condenser 33 exchanges heat between the heat medium supplied by the compressor 32 and the cool air from the interior of the vehicle sent from the blower 36. That is, the air that has passed through the blower 36 is heated by heat exchange in the condenser 33 and is supplied to the interior of the vehicle as warm air for heating.

[0019] The expander 34 reduces the pressure of the heat medium that has passed through the condenser 33 before it flows into the chiller 35, thereby changing it into a low-temperature, low-pressure, gas-liquid two-phase state.

[0020] The second heat exchange circuit 2 includes a second pump 21, a charger 22, a DC-DC converter 23, a power train 24 (inverter 25, traction motor 26), a radiator 28, and a second tank 29, which are arranged in this order so that a heat medium (the same type of heat medium as in the first heat exchange circuit 1) circulates through them.

[0021] The second pump 21 pumps the heat medium stored in the second tank 29 toward the charger 22 .

[0022] The charger 22 is connected to an external charging facility (not shown) outside the electric vehicle and supplies power to the battery 12, or is connected to an electrical device (not shown) outside the electric vehicle and supplies power from the battery 12 to the electrical device (not shown), and is cooled by a heat medium.

[0023] The DC-DC converter 23, which steps down the DC voltage of the battery 12 and supplies it to the auxiliary devices that make up the electric vehicle, is cooled by a heat medium.

[0024] The inverter 25 converts the DC voltage of the battery 12 into AC voltage and supplies it to the traction motor 26, or when the traction motor 26 generates regenerative power, converts the regenerative power into DC voltage and supplies it to the battery 12. The inverter 25 has switching elements (a first switching element 251 and a second switching element 253 ( FIG. 4 )) described below, and exhaust heat is generated when these switching elements are driven. The exhaust heat is taken in by the heat medium, i.e., the first heat exchange circuit 1.

[0025] The traction motor 26 exchanges electric power with the inverter 25, and the exchange of electric power generates exhaust heat, which is also taken into the heat medium, i.e., the first heat exchange circuit 1. Note that the traction motor 26 can generate exhaust heat even when it is not rotating, for example, when a d-axis current is supplied to it.

[0026] The inverter 25 and the traction motor 26 are integrally formed as a power train 24 (PT, ePT), and are configured such that exhaust heat can be directly transferred between the inverter 25 and the traction motor 26 .

[0027] The radiator 28 exchanges heat between the heat medium that has passed through the powertrain 24 and the outside air, and supplies the heat medium after the heat exchange to the second tank 29 .

[0028] The second tank 29 stores the heat medium discharged from the radiator 28 .

[0029] An ePT temperature sensor 27 is disposed at a position downstream of the powertrain 24 in the second heat exchange circuit 2 , and outputs information on the temperature of the heat medium discharged from the powertrain 24 to the controller 100 .

[0030] The connecting mechanism 4 includes a first connecting passage 41 , a first control valve 42 , a second control valve 43 , a second connecting passage 44 , a third control valve 45 , and a fourth control valve 46 .

[0031] The first control valve 42 is an end of the first connecting flow path 41 on the first heat exchange circuit 1 side. The first control valve 42 is disposed at a position between the chiller 35 and the first tank 14 of the first heat exchange circuit 1.

[0032] The first control valve 42 has an inlet for the heat medium at the end connected to the chiller 35, and an outlet for the heat medium at the end connected to the first pump 11 and the end connected to the first connecting flow path 41. However, the outlet connected to the first connecting flow path 41 is normally closed.

[0033] The second control valve 43 is an end of the first connecting passage 41 on the second heat exchange circuit 2 side. The second control valve 43 is disposed at a position between the radiator 28 and the second tank 29 of the second heat exchange circuit 2.

[0034] The second control valve 43 has an end connected to the radiator 28 as an inlet for the heat medium of the second heat exchange circuit 2, an end connected to the first connecting flow path 41 as an inlet for the heat medium of the first connecting flow path 41 (first heat exchange circuit 1), and an end connected to the second tank 29 as an outlet for the heat medium. However, the inlet connected to the first connecting flow path 41 is normally closed.

[0035] The third control valve 45 is an end of the second connecting flow path 44 on the first heat exchange circuit 1 side. The third control valve 45 is disposed at a position between the chiller 35 of the first heat exchange circuit 1 and the battery 12 (battery temperature sensor 13).

[0036] The third control valve 45 has an end connected to the battery 12 side as a heat medium inlet for the first heat exchange circuit 1, an end connected to the second connecting flow path 44 side as a heat medium inlet for the second connecting flow path 44 (second heat exchange circuit 2), and an end connected to the chiller 35 side as a heat medium outlet. However, the inlet connected to the second connecting flow path 44 side is normally closed.

[0037] The fourth control valve 46 is the end of the second connecting flow path 44 on the second heat exchange circuit 2 side. The fourth control valve 46 is disposed in a position on the second heat exchange circuit 2 between the power train 24 (ePT temperature sensor 27) and the radiator 28.

[0038] The fourth control valve 46 has an inlet for the heat medium at the end connected to the powertrain 24, an outlet for the heat medium at the end connected to the radiator 28, and an outlet for the heat medium at the side connected to the second connecting flow path 44. However, the outlet connected to the second connecting flow path 44 is normally closed.

[0039] The controller 100 is configured by one or more computers including, for example, a central processing unit (CPU), a read-only memory (ROM), a random access memory (RAM), and an input / output interface (I / O interface). Furthermore, the controller 100 receives input from a battery temperature sensor 13 the temperature of the heat medium immediately after it is discharged from the battery 12 (the temperature of the battery 12), and from an ePT temperature sensor 27 the temperature of the heat medium immediately after it is discharged from the powertrain 24 (the temperature of the powertrain 24). Furthermore, the controller 100 receives input of temperature information of the switching elements (first switching element 251, second switching element 253 (FIG. 4)) of the inverter 25 and temperature information of a variable resistor unit 5 (FIG. 5), which will be described later.

[0040] As will be described later, the controller 100 controls the first control valve 42, the second control valve 43, the third control valve 45, and the fourth control valve 46. Furthermore, as will be described later, the controller 100 controls the variable resistance unit 5 (FIG. 6) connected to the first gate terminal 251g of the first switching element 251 (FIG. 4) of the inverter 25 and the second gate terminal 253g of the second switching element 253 (FIG. 4), and controls the dead time (FIGS. 6 and 7) of the drive voltages (first drive voltage, second drive voltage) output to the variable resistance unit 5.

[0041] [Heat Medium Distribution Path] Fig. 2 is a diagram showing the heat medium distribution path in normal operation, and Fig. 3 is a diagram showing the heat medium distribution path when the battery is heated.

[0042] As shown in FIG. 2 , the first heat exchange circuit 1 and the second heat exchange circuit 2 usually form circulation paths independent of each other, and there is no flow of heat medium between the first heat exchange circuit 1 and the second heat exchange circuit 2.

[0043] The controller 100 sets an ePT heat recovery flag to determine whether to warm up the battery 12 arranged in the first heat exchange circuit 1, and controls each control valve according to whether the ePT heat recovery flag is in an OFF state (a state in which warm-up is not performed) or an ON state (a state in which warm-up is performed). If the temperature of the battery 12 (the temperature detected by the battery temperature sensor 13) is equal to or higher than a predetermined threshold temperature (a first threshold temperature), it is determined that warm-up of the battery 12 is not necessary, and sets the ePT heat recovery flag to an OFF state.

[0044] At this time, the controller 100 opens the inlet on the chiller 35 side and the outlet on the first tank 14 side of the first control valve 42 while closing the outlet on the first connecting flow path 41 side, opens the inlet on the radiator 28 side and the outlet on the second tank 29 side of the second control valve 43 while closing the inlet on the first connecting flow path 41 side, opens the inlet on the battery 12 side and the outlet on the chiller 35 side of the third control valve 45 while closing the inlet on the second connecting flow path 44 side, and opens the inlet on the powertrain 24 side and the outlet on the radiator 28 side of the fourth control valve 46 while closing the outlet on the second connecting flow path 44 side.

[0045] However, when the temperature of the battery 12 falls below a predetermined threshold temperature (first threshold temperature), the output of the battery 12 decreases, so it is determined that warming up is necessary, and the ePT heat recovery flag is set to the ON state.

[0046] At this time, in order to warm up the battery 12 through the circulation path shown in Figure 4, the controller 100 opens the inlet on the chiller 35 side, the outlet on the first tank 14 side, and the outlet on the first connecting flow path 41 side of the first control valve 42, closes the inlet on the radiator 28 side of the second control valve 43 while opening the outlet on the second tank 29 side and the inlet on the first connecting flow path 41 side, opens the inlet on the battery 12 side, the outlet on the chiller 35 side, and the inlet on the second connecting flow path 44 side of the third control valve 45, and opens the inlet on the powertrain 24 side and the outlet on the second connecting flow path 44 side of the fourth control valve 46 while closing the outlet on the radiator 28 side.

[0047] When the temperature of the battery 12 subsequently reaches a second threshold temperature that is higher than the first threshold temperature, the controller 100 determines that warming up of the battery 12 is not necessary and sets the ePT heat recovery flag to the OFF state.

[0048] Even if the temperature of the battery 12 is equal to or higher than the first threshold temperature, when the temperature of the powertrain 24 (the temperature detected by the ePT temperature sensor 27) falls below a predetermined threshold temperature (third threshold temperature), the controller 100 determines that the efficiency of the powertrain 24 (travel motor 26) will decrease and that warming up is necessary, and sets the ePT heat recovery flag to the ON state. Thereafter, when the temperature of the powertrain 24 reaches a fourth threshold temperature that is higher than the third threshold temperature, the controller 100 determines that warming up of the powertrain 24 is not necessary, and sets the ePT heat recovery flag to the OFF state.

[0049] When the ePT heat recovery flag is on and the temperature of the switching elements (first switching element 251, second switching element 253 (Figure 4)) of the inverter 25 reaches a predetermined upper limit temperature, the controller 100 sets the ePT heat recovery flag to the off state, thereby reducing thermal damage to the switching elements.

[0050] [Circuit Diagram of Powertrain 24] Fig. 4 is a circuit diagram of the powertrain 24. As shown in Fig. 4, the powertrain 24 includes an inverter 25, a traction motor 26 connected to the AC side of the inverter 25, and a smoothing capacitor 255 connected to the DC side of the inverter 25, and the battery 12 is connected in parallel to the DC side of the inverter 25 together with the smoothing capacitor 255.

[0051] The inverter 25 is configured by connecting in series a parallel circuit of a first switching element 251 and a first feedback diode 252 and a parallel circuit of a second switching element 253 and a second feedback diode 254 to form series circuits for the U phase, V phase, and W phase, and these are connected in parallel to a smoothing capacitor 255 and the battery 12.

[0052] Here, the first switching element 251 and the second switching element 253 are configured by, for example, an IGBT (Insulated Gate Bipolar Transistor).

[0053] In inverter 25, the connection midpoint (UM) of the U-phase series circuit is connected to the U-phase coil of traction motor 26, the connection midpoint (VM) of the V-phase series circuit is connected to the V-phase coil of traction motor 26, and the connection midpoint (WM) of the W-phase series circuit is connected to the W-phase coil of traction motor 26.

[0054] A first drive voltage (PWM signal) is input to the first gate terminals 251g (three terminals) of the first switching elements 251, and a second drive voltage (PWM signal) is input to the second gate terminals 253g (three terminals) of the second switching elements 253, thereby converting the DC voltage of the battery 12 into an AC voltage and outputting it to the traction motor 26, and also converting the regenerative power generated by the traction motor 26 into a DC voltage and charging the battery 12.

[0055] The first gate terminal 251g of the first switching element 251 (U phase, V phase, W phase) and the second gate terminal 253g of the second switching element 253 (U phase, V phase, W phase) are each connected to a drive circuit (not shown).

[0056] The drive circuit (not shown) outputs a first drive voltage (U phase) to the first switching element 251 (U phase), outputs a first drive voltage (V phase) to the first switching element 251 (V phase), outputs a first drive voltage (W phase) to the first switching element 251 (W phase), outputs a second drive voltage (U phase) to the second switching element 253 (U phase), outputs the second drive voltage (V phase) to the second switching element 253 (V phase), and outputs the second drive voltage (W phase) to the second switching element 253 (W phase).

[0057] The first drive voltage is a signal that oscillates by switching between a low voltage (LOW, e.g., 0 V) ​​and a high voltage (HIGH, e.g., 15 V) that is higher than the low voltage at a predetermined cycle (see FIGS. 6 and 7). The second drive voltage is a signal that oscillates in the same manner as the first drive voltage, but oscillates in the opposite phase to the first drive voltage (see FIGS. 6 and 7).

[0058] [Variable Resistor Unit 5] Fig. 5 is a circuit diagram of the variable resistor unit 5. As shown in Fig. 5, the variable resistor unit 5 is connected to the first gate terminal 251g of the first switching element 251 and the second gate terminal 253g of the second switching element 253. The drive circuit (not shown) outputs a first drive voltage to the first gate terminal 251g of the first switching element 251 and outputs a second drive voltage to the second gate terminal 253g of the second switching element 253 via the variable resistor unit 5.

[0059] The variable resistance unit 5 includes a first resistance circuit 51 and a second resistance circuit 54. The first resistance circuit 51 is a series circuit of a first switch 52 and a first gate resistor 53, and the second resistance circuit 54 is a series circuit of a second switch 55 and a second gate resistor 56. The first resistance circuit 51 and the second resistance circuit 54 are connected in parallel at the first gate terminal 251g (second gate terminal 253g) side and the input side of the first drive voltage (second drive voltage).

[0060] The first gate resistor 53 and the second gate resistor 56 are made of a predetermined resistive material, but the second gate resistor 56 is a resistive element having a higher resistance value than the first gate resistor 53 .

[0061] The first switch 52 is capable of switching the connection state (on state, off state) between the first output terminal (not shown) of the first drive voltage of the drive circuit (not shown) and the first gate resistor 53, and is controlled to be on or off by the controller 100.

[0062] The second switch 55 is capable of switching the connection state (on state, off state) between the second output terminal (not shown) of the second drive voltage of the drive circuit (not shown) and the second gate resistor 56, and is controlled to be on or off by the controller 100.

[0063] When the ePT heat recovery flag is in the off state, the controller 100 sets the first switch 52 to the on state (a state in which the first output terminal (not shown) of the drive circuit (not shown) is conductive to the first gate resistor 53) and sets the second switch 55 to the off state (a state in which the first output terminal (not shown) of the drive circuit (not shown) is isolated from the first gate resistor 53).

[0064] Similarly, when the ePT heat recovery flag is in the off state, the controller 100 sets the first switch 52 to the on state (a state in which the second output terminal (not shown) of the drive circuit (not shown) is conductive to the first gate resistor 53) and sets the second switch 55 to the off state (a state in which the second output terminal (not shown) of the drive circuit (not shown) is isolated from the first gate resistor 53).

[0065] The controller 100 may set the second switch 55 to the ON state when the ePT heat recovery flag is OFF, thereby further reducing the combined resistance of the parallel circuit of the first resistor circuit 51 and the second resistor circuit 54.

[0066] When the ePT heat recovery flag is in the ON state, the controller 100 sets the first switch 52 to the OFF state and sets the second switch 55 to the ON state. As a result, the first drive voltage is applied to the first gate terminal 251g through the second gate resistor 56, which has a higher resistance value than the first gate resistor 53. The second drive voltage is also applied to the second gate terminal 253g through the second gate resistor 56, which has a higher resistance value than the first gate resistor 53. Therefore, when the ePT heat recovery flag is in the ON state, the variable resistor unit 5 has a higher resistance than the variable resistor unit 5 when the ePT heat recovery flag is in the OFF state.

[0067] [Dead Time] Fig. 6 is a time chart of the first drive voltage, the on / off state of the first switching element 251, the second drive voltage, and the on / off state of the second switching element 253 when the ePT heat recovery flag is in the off state. Fig. 7 is a time chart of the first drive voltage, the on / off state of the first switching element 251, the second drive voltage, and the on / off state of the second switching element 253 when the ePT heat recovery flag is in the on state.

[0068] In order to prevent the first switching element 251 and the second switching element 253 from being turned on at the same time, i.e., to prevent the inverter 25 from being short-circuited, the controller 100 sets the dead time so that the time period when the first drive voltage is HIGH and the time period when the second drive voltage is HIGH do not overlap each other.

[0069] The controller 100 sets the first response time from when the first drive voltage switches from HIGH to LOW until the first switching element 251 switches from an ON state to an OFF state as the dead time from when the first drive voltage switches from HIGH to LOW until the second drive voltage switches from LOW to HIGH.

[0070] The controller 100 sets the second response time from when the second drive voltage switches from HIGH to LOW until the second switching element 253 switches from an ON state to an OFF state as the dead time from when the second drive voltage switches from LOW to HIGH until the first drive voltage switches from LOW to HIGH.

[0071] If the first switching element 251 and the second switching element 253 have the same characteristics, the first response time and the second response time will be the same.

[0072] Therefore, the controller 100 can prevent a short circuit of the inverter 25 by setting one dead time. If the first response time and the second response time are different from each other, two dead times of different lengths are set to correspond to the first response time and the second response time, respectively.

[0073] Incidentally, the first response time and the second response time become longer as the resistance value (gate resistance) of the variable resistance unit 5 connected to the first gate terminal 251g (second gate terminal 253g) increases. Therefore, the dead time for preventing the first switching element 251 and the second switching element 253 from being simultaneously conductive also needs to be set based on the first response time and the second response time.

[0074] Therefore, when the ePT heat recovery flag is in the OFF state and the variable resistance unit 5 has a low resistance as shown in Fig. 5, the controller 100 sets the dead times (DT1a, DT1b) as shown in Fig. 6. Also, when the ePT heat recovery flag is in the ON state and the variable resistance unit 5 has a high resistance as shown in Fig. 5, the controller 100 sets the dead times (DT2a, DT2b) as shown in Fig. 7.

[0075] Here, the dead times DT1a and DT1b are the same in length, the dead times DT2a and DT2b are the same in length, and the dead times DT12a and DT2b are longer than the dead times DT1a and DT1b.

[0076] 6 , during the dead time (DT1a) immediately after the first drive voltage is switched from HIGH to LOW, the first drive voltage and the second drive voltage are LOW. Meanwhile, the emitter-collector current of the first switching element 251 monotonically decreases from the emitter-collector current when the first switching element 251 is ON, and transitions to zero when the first switching element 251 is OFF. Therefore, the integral of the emitter-collector current of the first switching element 251 during the dead time (DT1a) becomes the first loss (heat amount) of the first switching element 251.

[0077] Similarly, during the dead time (DT1b) immediately after the second drive voltage is switched from HIGH to LOW, the first drive voltage and the second drive voltage are both LOW. Meanwhile, the emitter-collector current of the second switching element 253 monotonically decreases from the emitter-collector current when the second switching element 253 is ON, and transitions to zero when the second switching element 253 is OFF. Therefore, the integral of the emitter-collector current of the second switching element 253 during the dead time (DT1b) becomes the second loss (heat amount) of the second switching element 253.

[0078] 7 , during the dead time (DT2a) immediately after the first drive voltage is switched from HIGH to LOW, the first drive voltage and the second drive voltage are both LOW. Meanwhile, the emitter-collector current of the first switching element 251 monotonically decreases from the emitter-collector current when the first switching element 251 is ON, and transitions to zero when the first switching element 251 is OFF. Therefore, the integral of the emitter-collector current of the first switching element 251 during the dead time (DT2a) becomes the third loss (heat amount) of the first switching element 251.

[0079] Similarly, during the dead time (DT2b) immediately after the second drive voltage switches from HIGH to LOW, the first drive voltage and the second drive voltage are both LOW. Meanwhile, the emitter-collector current of the second switching element 253 monotonically decreases from the emitter-collector current when the second switching element 253 is ON, and transitions to zero when the second switching element 253 is OFF. Therefore, the integral of the emitter-collector current of the second switching element 253 during the dead time (DT2b) becomes the fourth loss (heat amount) of the second switching element 253.

[0080] Since the dead times (DT2a, DT2b) are longer than the dead times (DT1a, DT1b), the third loss is greater than the first loss, and the fourth loss is greater than the second loss.

[0081] Therefore, the heat generation amounts of the first switching element 251 and the second switching element 253 when the ePT heat recovery flag is set to the ON state are greater than the heat generation amounts of the first switching element 251 and the second switching element 253 when the ePT heat recovery flag is set to the ON state. This promotes heating of the heat medium circulating through the second heat exchange circuit 2, thereby enabling the warm-up of the powertrain 24, and furthermore, by supplying the heat medium to the first heat exchange circuit 1, the warm-up of the battery 12 can also be achieved.

[0082] [Control Flow When Warming Up of Battery 12 Begins] FIG. 8 is a flow diagram when warming up of the battery 12 begins in the thermal management system TM according to this embodiment.

[0083] In the initial state of the thermal management system TM, the ePT heat recovery flag is set to the off state, the heat medium flow path is the flow path shown in Figure 2, the first switch 52 (Figure 5) is set to the on state, the second switch 55 (Figure 5) is set to the off state, and the dead time is set to the dead time (DT1) (= DT1a, DT1b).

[0084] In step S801, the controller 100 acquires information on the temperature of the battery 12.

[0085] In step S802, the controller 100 determines whether the temperature of the battery 12 is lower than the first threshold temperature. If YES, the controller 100 proceeds to step S803, and if NO, the controller 100 returns to step S801.

[0086] In step S803, the controller 100 sets the ePT heat recovery flag to ON, thereby switching the heat medium flow path from the flow path shown in FIG.

[0087] In step S804, the controller 100 switches the dead time from the dead time (DT1) to the dead time (DT2) (=DT2a, DT2b).

[0088] In step S805, the controller 100 sets the first switch 52 (FIG. 5) to the OFF state and sets the second switch 55 (FIG. 5) to the ON state.

[0089] In FIG. 8, step S805 is executed after step S804, but steps S803, S804, and S805 may be executed simultaneously.

[0090] [Control flow when warm-up of battery 12 is stopped] Fig. 9 is a flow diagram of the thermal management system TM according to this embodiment when warm-up of battery 12 is stopped. The control flow shown in Fig. 9 is executed after the control flow shown in Fig. 8 is executed.

[0091] In step S901 , the controller 100 acquires information on the temperature of the battery 12 .

[0092] In step S902, the controller 100 determines whether the temperature of the battery 12 has reached a second threshold temperature that is higher than the first threshold temperature. If YES, the controller 100 proceeds to step S903, and if NO, the controller 100 returns to step S901.

[0093] In step S903, the controller 100 sets the ePT heat recovery flag to the OFF state, thereby switching the heat medium flow path from the flow path shown in FIG.

[0094] In step S904, the controller 100 sets the first switch 52 (FIG. 5) to the ON state and the second switch 55 (FIG. 5) to the OFF state.

[0095] In step S905, the controller 100 switches the dead time from the dead time (DT2) to the dead time (DT1).

[0096] In FIG. 9, step S905 is executed after step S904, but steps S903, S904, and S905 may be executed simultaneously.

[0097] [Temperature of Variable Resistor Unit 5 and Dead Time] Figure 10 is a diagram showing the relationship between the temperature of the variable resistor unit 5 and the dead time. The first gate resistor 53 (Figure 5) and the second gate resistor 56 (Figure 5) that make up the variable resistor unit 5 are made of a resistive material, and the resistivity of resistive materials generally increases with increasing temperature. Therefore, the resistance values ​​of the first gate resistor 53 (Figure 5) and the second gate resistor 56 (Figure 5) increase with increasing temperature, which lengthens the first response time of the first switching element 251 and the second response time of the second switching element 253. Therefore, the dead times set corresponding to the first response time of the first switching element 251 and the second response time of the second switching element 253 also need to be lengthened.

[0098] Therefore, in this embodiment, a temperature sensor (not shown) may be attached to the variable resistance unit 5, and the controller 100 may acquire the temperature of the variable resistance unit 5 and set the dead time (DT1) and the dead time (DT2) based on the acquired temperature and the map shown in Fig. 9. This allows the dead time to be set just right in response to changes due to temperature dependency in the first response time of the first switching element 251 and the second response time of the second switching element 253.

[0099] 11 is a diagram showing a modified example of variable resistance unit 5. Variable resistance unit 5 of the modified example includes a third gate resistor 57, a slider 58 that is in contact with third gate resistor 57 and is slidable in the direction of current flow through third gate resistor 57 (the direction in which the resistance between slider 58 and first gate terminal 251g (second gate terminal 253g) changes) while in contact with third gate resistor 57, and an actuator (not shown) that moves slider 58 in the direction of current flow through third gate resistor 57 (low resistance side, high resistance side).

[0100] With respect to the variable resistance unit 5 connected to the first switching element 251, the third gate resistor 57 is connected to the first gate terminal 251g of the first switching element 251. The tip of the slider 58 contacts the third gate resistor 57, and the base end of the slider 58 is connected to a first output terminal (not shown) that outputs a first drive voltage of a drive circuit (not shown).

[0101] With respect to the variable resistance unit 5 connected to the second switching element 253, the third gate resistor 57 is connected to the second gate terminal 253g of the second switching element 253. The tip of the slider 58 is in contact with the third gate resistor 57, and the base end of the slider 58 is connected to a second output terminal (not shown) that outputs a second drive voltage of the drive circuit (not shown).

[0102] When the ePT heat recovery flag is in the off state, the controller 100 moves the slider 58 to the low resistance side (in the direction toward the first gate terminal 251g (second gate terminal 253g)) via an actuator (not shown), and when the ePT heat recovery flag is in the on state, the controller 100 moves the slider 58 to the high resistance side (in the direction away from the first gate terminal 251g (second gate terminal 253g)) via an actuator (not shown).

[0103] [Effects of this embodiment] The thermal management method for an electric vehicle of this embodiment is a thermal management method for an electric vehicle equipped with a waste heat circulation path (first heat exchange circuit 1) that takes in waste heat from an inverter 25 that exchanges power with a traction motor 26 that drives the electric vehicle, in which drive voltages (first drive voltage, second drive voltage) that drive switching elements (first switching element 251, second switching element 253) that constitute the inverter 25 are applied to gate terminals (first gate terminal 251g, second gate terminal 253g) of the switching elements (first switching element 251, second switching element 253) via a variable resistance unit 5, and the resistance value of the variable resistance unit 5 when the waste heat stored in the waste heat circulation path (first heat exchange circuit 1) is supplied to the outside is set to be higher than the resistance value of the variable resistance unit 5 before the waste heat is supplied to the outside.

[0104] With the above method, increasing the resistance value of variable resistance unit 5 increases the loss of inverter 25, and therefore, by increasing the loss of inverter 25 when supplying exhaust heat to the outside, the amount of exhaust heat from inverter 25 is increased, and the exhaust heat can be efficiently supplied to the outside. Therefore, this is a thermal management method for an electric vehicle that can efficiently extract exhaust heat from inverter 25 when supplying the exhaust heat to the outside of the exhaust heat circulation path (first heat exchange circuit 1).

[0105] In the present embodiment, the variable resistance unit 5 includes a first resistance circuit 51 that includes a first gate resistor 53 and applies drive voltages (first drive voltage, second drive voltage) to the gate terminals (first gate terminal 251g, second gate terminal 253g) through the first gate resistor 53, and a second resistance circuit 54 that is connected in parallel with the gate terminals (first gate terminal 251g, second gate terminal 253g) together with the first resistance circuit 51 and includes a second gate resistor 56 that has a higher resistance value than the first gate resistor 53 and applies the drive voltages (first drive voltage, second drive voltage) to the gate terminals through the second gate resistor 56, and the first resistance circuit 51 (first switch 52) is set to an ON state before the exhaust heat is supplied to the outside, and when the exhaust heat is supplied to the outside, the first resistance circuit 51 (first switch 52) is set to an OFF state and the second resistance circuit 54 (second switch 55) is set to an ON state.

[0106] By the above method, the resistance value of the variable resistance section 5 can be changed in a simple manner.

[0107] In this embodiment, the switching elements (first switching element 251, second switching element 253) are arranged in pairs and connected in series, and the drive voltages (first drive voltage, second drive voltage) are determined by applying a first drive voltage to the gate terminal of one (first switching element 251) of the pair of switching elements (first switching element 251, second switching element 253) and a second drive voltage to the gate terminal (first gate terminal 251g, second gate terminal 251g) of the other (second switching element 253) of the pair of switching elements (first switching element 251, second switching element 253). and a second drive voltage applied to the first switching element 251 and the second switching element 253 (terminal 253g), and in the case where a dead time (DT1, DT2) is set between the first drive voltage and the second drive voltage to prevent a pair of switching elements (first switching element 251, second switching element 253) from being simultaneously turned on, the dead time (DT2) when the first resistance circuit 51 (first switch 52) is set to the off state and the second resistance circuit 54 (second switch 55) is set to the on state is set longer than the dead time (DT1) when the first resistance circuit 51 (first switch 52) is in the on state.

[0108] By using the above method, the dead times (DT1, DT2) can be appropriately set in accordance with the response time (response speed) of the switching element in response to changes in the gate resistance.

[0109] In this embodiment, the switching elements (first switching element 251, second switching element 253) include a first switching element 251 including a first gate terminal 251g, and a second switching element 253 including a second gate terminal 253g different from the first gate terminal 251g and connected in series with the first switching element 251. A connection midpoint (UM, VM, WM) between the first switching element 251 and the second switching element 253 is connected to the traction motor 26, and a drive voltage (first drive The first driving voltage, the second driving voltage) includes a first driving voltage applied to the first gate terminal 251g while alternately switching the voltage between a low voltage (LOW) and a high voltage (HIGH) higher than the low voltage (LOW) at a predetermined period, and a second driving voltage applied to the second gate terminal 253g while alternately switching the voltage between a low voltage (LOW) and a high voltage (HIGH) in an opposite phase to the first driving voltage, and the first driving voltage and the second driving voltage are switched in order to prevent the first switching element 251 and the second switching element 253 from being simultaneously turned on. In the case where dead times (DT1, DT2) are set during which the two drive voltages are simultaneously set to a low voltage (LOW), the response time (first response time) is the time from when the first drive voltage is switched from a high voltage (HIGH) to a low voltage (LOW) when the first resistor circuit 51 (first switch 52) is in the on state until the first switching element 251 is switched from the on state to the off state, or the time from when the second drive voltage is switched from a high voltage (HIGH) to a low voltage (LOW) when the first resistor circuit 51 (first switch 52) is in the on state until the first switching element 251 is switched from the on state to the off state. a dead time (DT1) is set based on a response time (second response time) from when the first drive voltage is switched to when the second switching element 253 is switched from the on state to the off state, and a response time (first response time) from when the first drive voltage is switched from a high voltage (HIGH) to a low voltage (LOW) to when the first switching element 251 is switched from the on state to the off state when the first resistor circuit 51 (first switch 52) is set to the off state and the second resistor circuit 54 (second switch 55) is set to the on state;Alternatively, when the first resistor circuit 51 (first switch 52) is set to the OFF state and the second resistor circuit 54 (second switch 55) is set to the ON state, the dead time (DT2) is set based on the response time (second response time) from when the second drive voltage is switched from a high voltage (HIGH) to a low voltage (LOW) until the second switching element 253 is switched from an ON state to an OFF state.

[0110] By using the above method, the dead time (DT1, DT2) is set in accordance with the change in the response time (response speed) of the switching element accompanying the change in the resistance value of the variable resistor section 5, and just the right amount of loss can be generated in the inverter 25.

[0111] In this embodiment, the resistance value of the variable resistance unit 5 (first gate resistor 53, second gate resistor 56) is estimated based on the temperature of the variable resistance unit 5 (first gate resistor 53, second gate resistor 56), and the dead time (DT1, DT2) is estimated based on the estimated resistance value.

[0112] By using the above method, the dead time (DT1, DT2) can be set with high precision in accordance with the response time (response speed) of the switching element due to temperature changes in the resistance value of the variable resistance section 5 (first gate resistor 53, second gate resistor 56).

[0113] In this embodiment, when exhaust heat is supplied from the exhaust heat circulation path (first heat exchange circuit 1) to the device to be warmed up (battery 12), after the exhaust heat is supplied to the device to be warmed up (battery 12), when the temperature of the device to be warmed up (first heat exchange circuit 1) reaches a predetermined threshold temperature (second threshold temperature), the first resistance circuit 51 is set to the on state.

[0114] By using the above method, it is possible to reduce the power consumption of the battery 12 when power is supplied from the battery 12 to the inverter 25 .

[0115] In this embodiment, when exhaust heat is supplied from the exhaust heat circulation path (first heat exchange circuit 1) to the device to be warmed up (battery 12), if the temperature of the device to be warmed up (battery 12) is lower than a predetermined first threshold temperature, the supply of exhaust heat from the exhaust heat circulation path (first heat exchange circuit 1) to the device to be warmed up (battery 12) is started, the first resistance circuit 51 is set to an off state, and the second resistance circuit 54 is set to an on state; when the temperature of the device to be warmed up (battery 12) reaches a second threshold temperature that is higher than the first threshold temperature, the supply of exhaust heat from the exhaust heat circulation path (first heat exchange circuit 1) to the device to be warmed up (battery 12) is stopped, and the first resistance circuit 51 is set to an on state.

[0116] By using the above method, the temperature of the battery 12 can be maintained at an appropriate temperature at which the output of the battery 12 does not decrease, and the power consumption of the battery 12 can be reduced when power is being supplied from the battery 12 to the inverter 25 .

[0117] In this embodiment, the switching elements (first switching element 251, second switching element 253) are arranged in pairs and connected in series, and the drive voltages (first drive voltage, second drive voltage) include a first drive voltage applied to a gate terminal (first gate terminal 251g) of one (first switching element 251) of the pair of switching elements (first switching element 251, second switching element 253) and a second drive voltage applied to a gate terminal (second gate terminal 253g) of the other (second switching element 253) of the pair of switching elements (first switching element 251, second switching element 253). When dead times (DT1, DT2) are set between the first drive voltage and the second drive voltage to prevent the switching elements (first switching element 251, second switching element 253) from being simultaneously conductive, the dead time (DT2) when supplying exhaust heat to the device to be warmed up (battery 12) is set to be longer than the dead time (DT) before supplying exhaust heat to the device to be warmed up (battery 12), and the dead time after stopping the supply of exhaust heat from the exhaust heat circulation path (first heat exchange circuit 1) to the device to be warmed up (battery 12) is then set to the dead time (DT) before supplying exhaust heat to the device to be warmed up (battery 12).

[0118] With the above method, the dead times (DT1, DT2) are set in response to the change in the response time (response speed) of the switching elements (first switching element 251, second switching element 253) that accompanies the change in the resistance value of the variable resistance unit 5, and it is possible to generate just the right amount of loss for the inverter 25. Furthermore, when power is being supplied from the battery 12 to the inverter 25, it is possible to reduce the power consumption of the battery 12.

[0119] In this embodiment, when the first resistance circuit 51 is in the off state and the second resistance circuit 54 is in the on state, if the temperature of the switching elements (first switching element 251, second switching element 253) reaches a predetermined upper limit temperature, the first resistance circuit 51 is set to the on state.

[0120] By using the above method, the first resistor circuit 51 is set to the on state and the response time (response speed) of the switching elements (first switching element 251, second switching element 253) is shortened, thereby reducing loss in the switching elements (first switching element 251, second switching element 253). This makes it possible to suppress temperature increases due to loss in the switching elements (first switching element 251, second switching element 253) and reduce thermal damage to the switching elements (first switching element 251, second switching element 253).

[0121] In this embodiment, the switching elements (first switching element 251, second switching element 253) are arranged in pairs and connected in series, and the driving voltages (first driving voltage, second driving voltage) are a first driving voltage applied to a gate terminal (first gate terminal 251g) of one (first switching element 251) of the pair of switching elements (first switching element 251, second switching element 253), and a second driving voltage applied to the gate terminal of the other (first switching element 251, second switching element 253). and a second drive voltage applied, and in the case where a dead time (DT1, DT2) is set between the first drive voltage and the second drive voltage to prevent a pair of switching elements (first switching element 251, second switching element 253) from being simultaneously turned on, the dead time (DT2) when the exhaust heat is supplied to the outside is set to be longer than the dead time (DT1) before the exhaust heat is supplied, and thereafter, when the first resistor circuit 51 is set to the on state, the dead time is set to the dead time (DT1) before the exhaust heat is supplied to the outside.

[0122] With the above configuration, the dead times (DT1, DT2) are set in response to the change in the response time (response speed) of the switching elements (first switching element 251, second switching element 253) accompanying the change in the resistance value of the variable resistance unit 5, and it is possible to generate just the right amount of loss for the inverter 25. Furthermore, when power is supplied from the battery 12 to the inverter 25, it is possible to reduce the power consumption of the battery 12.

[0123] The thermal management system TM for an electric vehicle of this embodiment is a thermal management system TM for an electric vehicle that includes a waste heat circulation path (first heat exchange circuit 1) that takes in waste heat from an inverter 25 that exchanges power with a traction motor 26 that drives the electric vehicle, and includes a drive circuit (not shown) that outputs drive voltages (first drive voltage, second drive voltage) that drive switching elements (first switching element 251, second switching element 253) that constitute the inverter 25, a variable resistance unit 5 that is arranged between the gate terminals (first gate terminal 251g, second gate terminal 253g) of the switching elements (first switching element 251, second switching element 253), and a control unit (controller 100) that controls the variable resistance unit 5, and the control unit (controller 100) sets the resistance value of the variable resistance unit 5 when the waste heat stored in the waste heat circulation path (first heat exchange circuit 1) is supplied to the outside to be higher than the resistance value of the variable resistance unit 5 before the waste heat is supplied to the outside.

[0124] With the above configuration, increasing the resistance value of the variable resistance unit 5 increases the loss of the inverter 25, and therefore, by increasing the loss of the inverter 25 when supplying the exhaust heat to the outside, the amount of exhaust heat from the inverter 25 is increased, and the exhaust heat can be efficiently supplied to the outside. Therefore, the thermal management system TM for an electric vehicle can efficiently extract exhaust heat from the inverter 25 when supplying the exhaust heat to the outside of the exhaust heat circulation path (first heat exchange circuit 1).

[0125] Although the embodiments of the present invention have been described above, the above embodiments merely illustrate some of the application examples of the present invention, and it is not intended that the technical scope of the present invention be limited to the specific configurations of the above embodiments.

Claims

1. A thermal management method for an electric vehicle equipped with a heat exhaust circulation path that takes in exhaust heat from an inverter that exchanges power with a traction motor that drives the electric vehicle, the method comprising: applying a drive voltage that drives a switching element that constitutes the inverter to a gate terminal of the switching element via a variable resistor; and setting the resistance value of the variable resistor when the exhaust heat stored in the heat exhaust circulation path is supplied to the outside to be higher than the resistance value of the variable resistor before the exhaust heat is supplied to the outside.

2. The thermal management method for an electric vehicle according to claim 1, wherein the variable resistance unit includes: a first resistance circuit including a first gate resistor and applying the drive voltage to the gate terminal through the first gate resistor; and a second resistance circuit connected in parallel to the gate terminal together with the first resistance circuit, including a second gate resistor having a higher resistance value than the first gate resistor, and applying the drive voltage to the gate terminal through the second gate resistor; the first resistance circuit is set to an ON state before the exhaust heat is supplied to the outside; and when the exhaust heat is supplied to the outside, the first resistance circuit is set to an OFF state and the second resistance circuit is set to an ON state.

3. The thermal management method for an electric vehicle according to claim 2, wherein the switching elements are arranged in pairs and connected in series, the drive voltages include a first drive voltage applied to the gate terminal of one of the pair of switching elements and a second drive voltage applied to the gate terminal of the other of the pair of switching elements, and when a dead time is set between the first drive voltage and the second drive voltage to prevent the pair of switching elements from being simultaneously conductive, the dead time when the first resistance circuit is set to an off state and the second resistance circuit is set to an on state is set longer than the dead time when the first resistance circuit is in an on state.

4. The switching elements include a first switching element including a first gate terminal, and a second switching element including a second gate terminal different from the first gate terminal and connected in series with the first switching element, a connection midpoint between the first switching element and the second switching element is connected to the traction motor, the drive voltages include a first drive voltage applied to the first gate terminal while alternately switching the voltage between a low voltage and a high voltage higher than the low voltage at a predetermined cycle, and a second drive voltage applied to the second gate terminal while alternately switching the voltage between the low voltage and the high voltage in an opposite phase to the first drive voltage, when a dead time is set during which the first drive voltage and the second drive voltage simultaneously become the low voltage in order to prevent the first switching element and the second switching element from being simultaneously conductive, 3. The thermal management method for an electric vehicle according to claim 2, wherein the dead time is set based on a response time from when the first drive voltage is switched from the high voltage to the low voltage to when the first switching element is switched from an on state to an off state when the first resistor circuit is in an on state, or a response time from when the second drive voltage is switched from the high voltage to the low voltage to when the second switching element is switched from an on state to an off state when the first resistor circuit is in an on state; or a response time from when the first drive voltage is switched from the high voltage to the low voltage to when the first switching element is switched from an on state to an off state when the first resistor circuit is set in an off state and the second resistor circuit is set in an on state, or a response time from when the second drive voltage is switched from the high voltage to the low voltage to when the second switching element is switched from an on state to an off state when the first resistor circuit is set in an off state and the second resistor circuit is set in an on state.

5. A thermal management method for an electric vehicle according to claim 3 or 4, wherein the resistance value of the variable resistor section is estimated based on the temperature of the variable resistor section, and the dead time is estimated based on the estimated resistance value.

6. A thermal management method for an electric vehicle as described in claim 2, wherein, when the exhaust heat is supplied from the exhaust heat circulation path to a device to be warmed up, after the exhaust heat is supplied to the device to be warmed up, when the temperature of the device to be warmed up reaches a predetermined threshold temperature, the first resistance circuit is set to an on state.

7. A thermal management method for an electric vehicle as described in claim 2, wherein, when the exhaust heat is supplied from the exhaust heat circulation path to a device to be warmed up, if the temperature of the device to be warmed up is lower than a predetermined first threshold temperature, the supply of the exhaust heat from the exhaust heat circulation path to the device to be warmed up is started, the first resistance circuit is set to an off state, and the second resistance circuit is set to an on state; and when the temperature of the device to be warmed up reaches a second threshold temperature that is higher than the first threshold temperature, the supply of the exhaust heat from the exhaust heat circulation path to the device to be warmed up is stopped, and the first resistance circuit is set to an on state.

8. A thermal management method for an electric vehicle as set forth in claim 6 or claim 7, wherein the switching elements are arranged in pairs and connected in series, the drive voltage includes a first drive voltage applied to the gate terminal of one of the pair of switching elements and a second drive voltage applied to the gate terminal of the other of the pair of switching elements, and when a dead time is set between the first drive voltage and the second drive voltage to prevent the pair of switching elements from being simultaneously conductive, the dead time when the exhaust heat is supplied to the device to be warmed up is set to be longer than the dead time before the exhaust heat is supplied to the device to be warmed up, and thereafter the dead time after the supply of the exhaust heat from the exhaust heat circulation path to the device to be warmed up is stopped is set to the dead time before the exhaust heat is supplied to the device to be warmed up.

9. A thermal management method for an electric vehicle as described in claim 2, wherein when the temperature of the switching element reaches a predetermined upper limit temperature while the first resistance circuit is in an off state and the second resistance circuit is in an on state, the first resistance circuit is set to an on state.

10. A thermal management method for an electric vehicle as set forth in claim 9, wherein the switching elements are arranged in pairs and connected in series, the drive voltage includes a first drive voltage applied to the gate terminal of one of the pair of switching elements and a second drive voltage applied to the gate terminal of the other of the pair of switching elements, and when a dead time is set between the first drive voltage and the second drive voltage to prevent the pair of switching elements from being simultaneously conductive, the dead time when the exhaust heat is supplied to the outside is set longer than the dead time before the exhaust heat is supplied, and thereafter, when the first resistance circuit is set to an on state, the dead time is set to the dead time before the exhaust heat is supplied to the outside.

11. A thermal management system for an electric vehicle equipped with a heat exhaust circulation path that takes in exhaust heat from an inverter that exchanges power with a traction motor that drives the electric vehicle, the system including: a variable resistance unit arranged between a drive circuit that outputs a drive voltage that drives a switching element that constitutes the inverter and a gate terminal of the switching element; and a control unit that controls the variable resistance unit, wherein the control unit sets the resistance value of the variable resistance unit when the exhaust heat stored in the heat exhaust circulation path is supplied to the outside to be higher than the resistance value of the variable resistance unit before the exhaust heat is supplied to the outside.

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