Power converter

Abstract

To reduce an amplitude of series voltage variation in a storage battery part while keeping a high effective value of AC current required for increasing a temperature of the storage battery part.SOLUTION: There are provided a first storage battery part and a second storage battery part, an inverter, a rotary electric machine, a connection passage for electrically connecting the rotary electric machine with an intermediate terminal between the first storage battery part and the second storage battery part, a control part for controlling a current flowing through the rotary electric machine and the connection passage by controlling a switching operation of the inverter, and an external connection terminal for connecting an external power supply with a series connection body. The control part has a temperature-raising mode in which the first storage battery part and the second storage battery part are temperature-raised by supplying a current to the intermediate terminal via the connection passage, and in the temperature-raising mode, a current command value of an AC component having a current waveform in a shape in which a difference between a maximum current value and a minimum current value in an AC fundamental wave period is smaller than a difference between a maximum value and a minimum value of a fundamental sine wave is calculated as the current command value of the AC component supplied to the intermediate terminal via the connection passage.SELECTED DRAWING: Figure 5

Description

[Technical Field]

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

[0002] Patent Document 1 listed below discloses a technology in which an alternating current is supplied to the neutral point between series-connected batteries in a power conversion device mounted on a vehicle, causing the batteries to generate heat through their internal resistance and raise the temperature of the batteries. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-175119 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the applicants have discovered that with the technology of Patent Document 1, if the above-mentioned battery heating operation is performed simultaneously with external charging of the battery by a charging stand, the series voltage fluctuation of the battery may exceed the allowable voltage fluctuation of the charging stand, and charging may not be able to continue. [Means for solving the problem]

[0005] In order to solve the above-described problems, a power conversion device according to one embodiment includes a first storage unit and a second storage unit forming a series-connected body, an inverter connected in parallel to the series-connected body, a rotating electric machine driven by current supplied from the inverter, a connection path electrically connecting the rotating electric machine and an intermediate terminal between the first storage unit and the second storage unit, a control unit that controls the current flowing through the rotating electric machine and the connection path by controlling the switching operation of the inverter, and an external connection terminal for connecting an external power source to the series-connected body, wherein the control unit has a temperature rise mode in which the first storage unit and the second storage unit are heated by supplying current to the intermediate terminal via the connection path, and in the temperature rise mode, calculates a command value for the AC component current to be supplied to the intermediate terminal via the connection path, the command value being an AC component current having a current waveform in which the difference between the maximum and minimum current values ​​within a fundamental wave period of the AC is smaller than the difference between the maximum and minimum values ​​of a fundamental sine wave. [Effects of the Invention]

[0006] According to an electric power conversion device according to one embodiment, the amplitude of series voltage fluctuation in the power storage unit can be reduced while maintaining a high effective value of the AC current required to increase the temperature of the power storage unit. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a diagram illustrating an example of a circuit configuration of a power conversion device according to an embodiment. [Figure 2] FIG. 1 is a diagram showing a simplified equivalent circuit of a power conversion device according to an embodiment in a temperature rise mode; [Figure 3] A diagram showing the electrical waveform when a sine wave current is applied in the temperature rise mode. [Figure 4] Diagram showing the mechanism of voltage fluctuations in the series connection of the energy storage unit when a sinusoidal current is applied [Figure 5] A diagram showing the differential waveform of the series voltage of the battery unit due to the AC current waveform in the temperature rise mode [Figure 6] FFT results for AC current [Figure 7] A diagram showing the differential waveform of the series voltage of the battery unit due to the AC current waveform in the temperature rise mode [Figure 8] Figure showing the results of FFT analysis of the series voltage of the storage battery [Figure 9] 10 is a flowchart showing an example of a procedure for calculating an AC current by a control device. [Figure 10] FIG. 2 is a diagram illustrating an example of the configuration of a current control system included in a power conversion device according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0009] (Circuit configuration of power conversion device 100) Fig. 1 is a diagram showing an example of a circuit configuration of a power conversion device 100 according to an embodiment. The power conversion device 100 shown in Fig. 1 is provided in a vehicle such as an electric vehicle or a hybrid vehicle.

[0010] As shown in FIG. 1, power conversion device 100 includes inverter 10, rotating electrical machine 20, first power storage unit 31, second power storage unit 32, voltage sensor 41, current sensor 51, smoothing capacitor 71, and control device 110.

[0011] The first power storage unit 31 and the second power storage unit 32 are so-called batteries, and store electric power for driving the rotating electric machine 20. The first power storage unit 31 and the second power storage unit 32 form a series connection, and the series connection is connected in parallel to the inverter 10. For example, secondary batteries such as lithium-ion batteries can be used as the first power storage unit 31 and the second power storage unit 32. The first power storage unit 31 has an internal resistance 31a. The second power storage unit 32 has an internal resistance 32a. The first power storage unit 31 and the second power storage unit 32 each have an output voltage of, for example, about 380 V. However, the output voltages of the first power storage unit 31 and the second power storage unit 32 may be any voltage. In the following description, the first power storage unit 31 and the second power storage unit 32 may be collectively referred to as the "power storage unit" or the like.

[0012] The inverter 10 is connected in parallel with the series-connected body formed by the first power storage unit 31 and the second power storage unit 32. The inverter 10 is configured to have a series-connected body of two switching elements Qxx for each of three phases (U phase, V phase, W phase). The inverter 10 converts DC current supplied from the series-connected body formed by the first power storage unit 31 and the second power storage unit 32 into AC current supplied to each phase (U phase, V phase, W phase) of the rotating electric machine 20 by the switching operation of the multiple switching elements Qxx.

[0013] The rotating electric machine 20 is a so-called three-phase AC motor. The rotating electric machine 20 has a U-phase winding 21U, a V-phase winding 21V, and a W-phase winding 21W. When current is supplied from the inverter 10 to each phase (U-phase, V-phase, W-phase), the rotating electric machine 20 rotates and generates drive torque for running the vehicle.

[0014] Voltage sensor 41 measures the voltage across the series connection formed by first power storage unit 31 and second power storage unit 32 (i.e., power storage unit series voltage Vbat12, which will be described later). Note that instead of voltage sensor 41, a configuration may be used in which the voltages of first power storage unit 31 and second power storage unit 32 are measured by a voltage sensor, and the sum of the voltages of first power storage unit 31 and second power storage unit 32 is calculated as the voltage across the series connection.

[0015] Current sensor 51 measures the current flowing through each phase (U phase, V phase, W phase) of rotating electric machine 20. Smoothing capacitor 71 smoothes the power supplied to inverter 10 from the series connection formed by first power storage unit 31 and second power storage unit 32. Smoothing capacitor 71 may be provided inside inverter 10.

[0016] The control device 110 is an example of a "control unit" and controls the switching operation (ON / OFF switching operation) of multiple switching elements Qxx of the inverter 10 based on the detection values ​​of each sensor, thereby controlling the current flowing from the inverter 10 to each phase of the rotating electric machine 20 and the current flowing from the rotating electric machine 20 to the connection path 60. The control device 110 is configured with, for example, a processor, a memory, etc., and can realize various functions by the processor executing programs stored in the memory. For example, the control device 110 is realized by an IC (Integrated Circuit).

[0017] The power conversion device 100 also includes a connection path 60. The connection path 60 electrically connects a neutral point O of the rotating electric machine 20 and an intermediate terminal B between the first power storage unit 31 and the second power storage unit 32. A switch 61 and a current sensor 52 are provided in the connection path 60. The switch 61 electrically connects and disconnects the connection path 60. The current sensor 52 measures the current flowing through the connection path 60. The control device 110 is capable of controlling the opening and closing operation of the switch 61. Note that neither the switch 61 nor the current sensor 52 are essential components. For example, instead of the current sensor 52, a configuration may be used in which the current sensor 51 measures each of the currents of the three phases of the rotating electric machine 20, and the sum of the measured currents of the three phases of the rotating electric machine 20 is calculated as the current flowing through the connection path 60.

[0018] Furthermore, power conversion device 100 has external connection terminals CH-1 and CL-1 in parallel with the series connection formed by first power storage unit 31 and second power storage unit 32. Power conversion device 100 is capable of rapid charging (e.g., 800V-DC rapid charging) first power storage unit 31 and second power storage unit 32 by being connected to a charger provided outside the vehicle via external connection terminals CH-1 and CL-1.

[0019] (heating mode) 2 is a diagram showing a simplified equivalent circuit of power conversion device 100 according to one embodiment in a temperature rise mode. Power conversion device 100 according to one embodiment has a temperature rise mode in which it raises the temperatures of first power storage unit 31 and second power storage unit 32 in cold weather, etc. In the temperature rise mode, control device 110 controls switch 61 to close, thereby electrically connecting neutral point O of rotating electric machine 20 to intermediate terminal B between first power storage unit 31 and second power storage unit 32.

[0020] The circuit configuration of the power conversion device 100 in the temperature rise mode can be expressed by a simplified equivalent circuit shown in Fig. 2 by combining the parallel configurations of the inverter 10 and the rotating electric machine 20 for each phase. The configuration shown in Fig. 2 is a buck-boost chopper configuration in which the current flowing through the winding 21 of the rotating electric machine 20 and the connection path 60 can be controlled by switching control of the inverter 10.

[0021] In the configuration shown in Figure 2, by performing switching control of inverter 10 (switching elements QH, QL) so that AC current flows through winding 21 of rotating electric machine 20 and connection path 60, AC current can be supplied to intermediate terminal B between first power storage unit 31 and second power storage unit 32, and therefore, Joule heat from internal resistances 31a, 32a can raise the temperatures of first power storage unit 31 and second power storage unit 32.

[0022] Fig. 3 shows the electrical waveforms when a sinusoidal current is passed through winding 21 of rotating electrical machine 20 and connection path 60 in the temperature rise mode. Fig. 3 shows the electrical waveforms when a sinusoidal current with an amplitude of I_a [A] and a frequency of F_r [Hz] is passed as AC current im through winding 21 of rotating electrical machine 20 and connection path 60 in the temperature rise mode.

[0023] At this time, the low-pass filter value obtained by removing the switching ripple component from the storage unit series voltage Vbat12, which is the output voltage of the series connection formed by the first storage unit 31 and the second storage unit 32, oscillates with an amplitude of ΔV_a [Vpp] and a frequency that is twice the frequency F_r of the sinusoidal current.

[0024] Here, when first power storage unit 31 and second power storage unit 32 are charged from an external charger via external connection terminals CH-1 and CL-1, if such a temperature increase operation is performed to increase the temperatures of first power storage unit 31 and second power storage unit 32, the above-mentioned voltage oscillation is applied to the external charger, which may cause the external charger to determine an abnormality and stop charging. Therefore, to avoid such a situation, it is necessary to sufficiently reduce the amplitude of power storage unit series voltage Vbat12.

[0025] (Mechanism of series voltage fluctuation in storage battery when sinusoidal current is applied) Fig. 4 is a diagram showing the mechanism of series voltage fluctuation of the power storage unit when a sinusoidal current is applied. Fig. 4 shows electrical behavior on a simplified equivalent circuit at timings t1, t2, t3, and t4 in Fig. 3. For simplicity of explanation, it is assumed that first power storage unit 31 and second power storage unit 32 have the same OCV (open circuit voltage) and internal resistance Rbat.

[0026] 4(a), at times t1 and t3, power storage unit series voltage Vbat12 reaches a maximum value. At these times, the current value of both first power storage unit 31 and second power storage unit 32 is close to 0 A. Therefore, a value close to the sum of the OCVs (open circuit voltages) of the power storage units is output as power storage unit series voltage Vbat12.

[0027] 4(b), at timing t2, the series voltage Vbat12 of the power storage unit reaches its minimum value, but current ibat1 of first power storage unit 31 is near its peak on the charging side (negative side), and current ibat2 of second power storage unit 32 is near its peak on the discharging side (positive side). At this time, on the charging side, voltage drop Rbat×ibat1 due to internal resistance Rbat [Ω] of the power storage unit acts to increase voltage Vbat1 of first power storage unit 31, and on the discharging side, Rbat×ibat2 acts to decrease voltage Vbat2 of second power storage unit 32. Here, assuming that loss is sufficiently small, according to the law of conservation of power, the power of the power storage units on both the charging side and the discharging side will be approximately the same value with the positive and negative signs reversed. Therefore, current ibat2 of second power storage unit 32 on the discharging side (lower voltage) will have a larger absolute value than current ibat1 of first power storage unit 31 on the charging side (higher voltage). Therefore, the negative voltage drop |Rbat2×ibat2| on the discharge side is larger than the positive voltage drop |Rbat1×ibat1| on the charge side, and therefore the series voltage Vbat12 of the power storage unit decreases relative to the sum of the OCVs.

[0028] As shown in Figure 4(c), at timing t4, the storage unit series voltage Vbat12 reaches its minimum value, but since this is the same as timing t2 except that the charging and discharging directions of the first storage unit 31 and the second storage unit 32 are reversed, the storage unit series voltage Vbat12 decreases relative to the sum of the OCVs.

[0029] Similarly, at other times, the voltage fluctuation due to the internal resistance Rbat [Ω] is in opposite phase on the charging side and the discharging side, resulting in a difference in the amplitude of the charging and discharging current, and the storage unit series voltage Vbat12 fluctuates at the second-order frequency of the sine wave current for heating.

[0030] Here, it can be seen that the difference between the maximum value (timings t1 and t3) and the minimum value (timings t2 and t4) of the storage unit series voltage Vbat12 is expressed as the absolute value of the difference in voltage drop due to the internal resistance Rbat [Ω] at the timing when the storage unit current is near the charging / discharging peak, i.e., Rbat1 × |ibat1 discharge peak vicinity value|-Rbat2 × |ibat2 charge peak vicinity value|, or Rbat2 × |ibat2 discharge peak vicinity value|-Rbat1 × |ibat1 charge peak vicinity value|.

[0031] That is, the greater the difference in amplitude between the charge and discharge currents, the greater the amplitude of series voltage Vbat12 of the power storage unit. Therefore, in order to reduce the amplitude of series voltage Vbat12 of the power storage unit while maintaining a high effective value of the AC current required for temperature increase, a method of reducing the difference in amplitude between the charge and discharge currents can be considered.

[0032] Fig. 5 shows differential waveforms of the series voltage of the power storage unit due to AC current waveforms in the temperature rise mode. Fig. 5(a) shows an electrical waveform when the command value of AC current im flowing through rotating electric machine 20 and connection path 60 is a sinusoidal current having only a first-order fundamental wave component. Fig. 5(b) shows an electrical waveform when the command value of AC current im flowing through rotating electric machine 20 and connection path 60 is an AC current to which a third-order harmonic component in phase with the fundamental wave component is applied.

[0033] 6A and 6B are diagrams showing the FFT results of the AC current im. Fig. 6A shows the FFT results of the AC current im when the command value of the AC current im flowing through the rotating electric machine 20 and the connection path 60 is a sinusoidal current having only a first-order fundamental wave component. Fig. 6B shows the FFT results of the AC current im when the command value of the AC current im flowing through the rotating electric machine 20 and the connection path 60 is an AC current to which a third-order harmonic component in phase with the fundamental wave component is applied.

[0034] As shown in Figures 5(a) and 6(a), when the command value of AC current im flowing through rotating electric machine 20 and connection path 60 is a sinusoidal current having only a first-order fundamental wave component, due to the mechanism described in Figure 4, series voltage fluctuations occur in the storage unit (series connection formed by first storage unit 31 and second storage unit 32) having amplitudes due to the difference between charging and discharging currents and voltage drops caused by internal resistance.

[0035] 5(b) and 6(b), when the command value of AC current im flowing through rotating electric machine 20 and connection path 60 is set to an AC current to which a third-order harmonic component in phase with the fundamental wave component is applied, AC current im has a trapezoidal current waveform with the peak of the sine wave current suppressed, thereby reducing the difference between the charge and discharge currents. Therefore, in the example shown in Fig. 5(b), the amplitude of the series voltage fluctuation in the power storage unit (the series-connected body formed by first power storage unit 31 and second power storage unit 32) is reduced due to the difference between the charge and discharge currents and the voltage drop caused by the internal resistance.

[0036] In this embodiment, a trapezoidal waveform AC current im is generated by applying a third harmonic component having a phase close to that of the fundamental wave component to the command value of the AC current im. However, other harmonic components (e.g., third, fifth, seventh, etc.) may be included in the command value of the AC current im as long as the effective value of the AC current required for temperature rise is kept high and the current shape reduces the difference in the amplitude of the charging and discharging currents.

[0037] In addition, the waveform shape of the command value of the AC current im may be determined by, for example, designing and mapping a waveform shape at a reference current effective value in advance, and calculating the waveform shape proportionally according to the current effective value required for temperature rise.

[0038] As described above, the power conversion device 100 according to one embodiment has a temperature rise mode in which the control device 110 raises the temperatures of the first and second storage units 31 and 32 by supplying a current to the intermediate terminal B via the connection path 60, and in the temperature rise mode, the control device 110 calculates, as a command value for the AC component current to be supplied to the intermediate terminal B via the connection path 60, a current waveform having a shape in which the difference between the maximum and minimum current values ​​within the fundamental wave period of the AC is smaller than the difference between the maximum and minimum values ​​of the fundamental sine wave.

[0039] This allows power conversion device 100 according to an embodiment to reduce the difference between the charge and discharge current amplitudes while maintaining a high effective value of the AC current required to increase the temperatures of first power storage unit 31 and second power storage unit 32. As a result, power conversion device 100 according to an embodiment can reduce the amplitude of series voltage fluctuations in the power storage unit (the series-connected body formed by first power storage unit 31 and second power storage unit 32).

[0040] In the power conversion device 100 according to one embodiment, the control device 110 may calculate a command value for a current of an AC component having at least odd-order harmonic components whose effective amplitude value is smaller than that of the fundamental sine wave in the temperature rise mode.

[0041] This allows power conversion device 100 according to an embodiment to reduce the difference between the charge and discharge current amplitudes while maintaining a high effective value of the AC current required to increase the temperatures of first power storage unit 31 and second power storage unit 32. As a result, power conversion device 100 according to an embodiment can reduce the amplitude of series voltage fluctuations in the power storage unit (the series-connected body formed by first power storage unit 31 and second power storage unit 32).

[0042] Fig. 7 is a diagram showing a differential waveform of the series voltage of the power storage unit due to an AC current waveform in a temperature rise mode, and Fig. 8 is a diagram showing the results of FFT analysis of the series voltage of the power storage unit.

[0043] 7(a) and 8(a) show differential waveforms of the series voltage of the power storage unit and FFT results of the series voltage of the power storage unit when AC current im flowing through rotating electric machine 20 and connection path 60 in the temperature rise mode is a sinusoidal current.

[0044] Figures 7(b) and 8(b) show the differential waveform of the series voltage of the storage unit and the FFT results of the series voltage of the storage unit when the AC current im flowing through the rotating electric machine 20 and the connection path 60 in the temperature rise mode is an AC current to which a third harmonic component having a phase close to that of the fundamental wave component is applied.

[0045] 7(c) and 8(c) show the differential waveform of the series voltage of the power storage unit and the FFT result of the series voltage of the power storage unit when the AC current im flowing through the rotating electric machine 20 and the connection path 60 in the temperature rise mode is a rectangular waveform AC current.

[0046] In this example, the transition time of the AC current im from near the maximum value on the positive side to near the maximum value on the negative side is gradually shortened in the order of the examples shown in Figures 7(a) and 8(a), the examples shown in Figures 7(b) and 8(b), and the examples shown in Figures 7(c) and 8(c).

[0047] As shown in Figure 7, it was found that as the transition time of the AC current im from near its maximum value on the positive side to near its maximum value on the negative side is gradually shortened, the duration during which fluctuations in the series voltage of the storage unit occur also gradually decreases.

[0048] Furthermore, as shown in Figure 8, when focusing on the FFT of the series voltage of the storage unit, it can be seen that the example shown in Figure 8(a) contains a large second-order component of the AC current, whereas the examples shown in Figures 8(b) and 8(c) have a reduced second-order component of the AC current and the voltage fluctuation component is dispersed on the high-frequency side.

[0049] 7(b) and 8(b) and the example shown in FIG. 7(c) and 8(c), in the power conversion device 100 according to an embodiment, the control device 110 calculates a command value for the current of the AC component in the temperature rise mode so that the transition time from near the maximum value on the positive side to near the maximum value on the negative side in the AC current im flowing through the rotating electric machine 20 and the connection path 60 has a waveform that is shorter than that of the fundamental sine wave (the example shown in FIG. 7(a) and 8(a)). As a result, the power conversion device 100 according to an embodiment can shorten the duration during which fluctuations occur in the series voltage of the power storage unit, and can reduce the low-frequency component in the AC current im.

[0050] As a result, for example, when suppressing voltage fluctuations using smoothing capacitor 71, a low-pass filter, or the like, it is possible to use smaller components with smaller capacitance or a higher cutoff frequency. Also, for example, when connecting to an external power source such as a charging stand, the voltage fluctuation component is attenuated by the low-pass filter in the voltage detection section on the external power source side, making it less likely that an abnormal voltage fluctuation will be detected erroneously, allowing stable continued charging.

[0051] (Example of procedure for calculating AC current im by control device 110) FIG. 9 is a flowchart showing an example of a procedure for the calculation process of the AC current im by the control device 110.

[0052] First, the control device 110 determines whether or not there is a request to increase the temperature of the power storage unit (step S1).

[0053] In step S1, if it is determined that there is no request to increase the temperature of the power storage unit (step S1: NO), control device 110 ends the series of processes shown in FIG.

[0054] In step S1, if it is determined that there is a request to increase the temperature of the storage unit (step S1: YES), the control device 110 sets the operating mode to a temperature increase mode, turns on (connects) the switch 61 on the connection path 60, and sets the effective value command of the AC current im flowing through the rotating electric machine 20 and the connection path 60 to a low amplitude (step S2).

[0055] Next, control device 110 determines whether the effective value command of AC current im is less than a predetermined value of the AC effective value (for example, a required value for quickly increasing the temperature of the power storage unit) (step S3).

[0056] In step S3, if it is determined that the effective value command of the AC current im is not less than the predetermined value of the AC current effective value (step S3: NO), the control device 110 advances the process to step S6.

[0057] In step S3, if it is determined that the effective value command of the AC current im is less than the predetermined value of the AC current effective value (step S3: YES), the control device 110 increases the effective value command in a stepwise manner and sets the AC current im based on the effective value command and a map (for example, a map of a trapezoidal waveform) (step S4), and supplies the AC current to the storage unit by switching control of the inverter 10.

[0058] Next, control device 110 determines whether the series voltage fluctuation of the power storage unit detected by voltage sensor 41 is equal to or greater than predetermined value A (step S5).

[0059] In step S5, if it is determined that the series voltage fluctuation of the power storage unit is not equal to or greater than a predetermined value A (a value that is smaller than the allowable value of voltage fluctuation with a margin) (step S5: NO), the control device 110 returns the process to step S3.

[0060] If it is determined in step S5 that the series voltage fluctuation of the power storage unit is equal to or greater than predetermined value A (step S5: YES), control device 110 advances the process to step S6.

[0061] In step S6, control device 110 determines whether or not the series voltage fluctuation of the power storage unit is equal to or less than predetermined value B (allowable value of voltage fluctuation) (step S6).

[0062] In step S6, if it is determined that the series voltage fluctuation of the storage unit is not equal to or less than the predetermined value B (step S6: NO), the control device 110 reduces the effective value command of the AC current im in order to reduce the voltage fluctuation, and sets the AC current im based on the effective value command and a map (for example, a map of a trapezoidal waveform shape) (step S7), then returns to step S6 and determines again whether the series voltage fluctuation of the storage unit is equal to or less than the predetermined value B.

[0063] If it is determined in step S6 that the series voltage fluctuation of the power storage unit is equal to or less than predetermined value B (step S6: YES), control device 110 ends the series of processes shown in FIG.

[0064] 9, the power conversion device 100 according to one embodiment detects the output voltage of the power storage unit in the temperature rise mode, and when the detected output voltage of the power storage unit exceeds a predetermined voltage fluctuation tolerance range (predetermined value B), the amplitude of the AC current im flowing through the rotating electric machine 20 and the connection path 60 can be reduced. Then, at the point in time when it is determined in step S6 that the series voltage fluctuation of the power storage unit is equal to or less than predetermined value B, the effective value of the AC current im can be set as large as possible within a range in which the series voltage fluctuation of the power storage unit does not exceed the tolerance value (predetermined value B).

[0065] In step S1, the control device 110 also determines whether an external power supply such as a charging stand is connected to the external connection terminals CH-1, CL-1. When an external power supply is not connected to the external connection terminals CH-1, CL-1, the allowable range of series voltage fluctuation of the power storage unit (i.e., the predetermined value A and the predetermined value B) may be larger than when an external power supply is connected to the external connection terminals CH-1, CL-1. In this way, when an external power supply is not connected to the external connection terminals CH-1, CL-1, the power conversion device 100 according to one embodiment allows a larger voltage fluctuation, thereby being able to supply a larger AC current to the power storage unit and therefore quickly raise the temperature of the power storage unit.

[0066] (Example of current control system configuration) FIG. 10 is a diagram showing an example of the configuration of a current control system included in the power conversion device 100 according to one embodiment.

[0067] In FIG. 10, Vdc represents the series voltage of the power storage unit. Im represents the connection path current. Id and Iq represent dq-axis currents in rotating electric machine 20. Vu, Vv, and Vw represent phase voltage commands. MVu, MVv, and MVw represent modulation commands. Sgu, Sgv, and Sgw represent carrier signals (e.g., triangular waves). QUH, QUL, QVH, QVL, QWH, and QWL represent gate signals of inverter switching elements.

[0068] The power conversion device 100 according to an embodiment can perform commonly known dq vector control when driving the rotating electric machine 20. Meanwhile, the power conversion device 100 according to an embodiment can perform PI control in a temperature rise mode so that the AC current im flowing through the connection path 60 follows a command value. Here, the command for the AC current im is calculated based on the flow of FIG. 9 , and the AC current im can be detected as the sum of three-phase current values ​​detected by the current sensor 52 or the current sensor 51.

[0069] Although the preferred embodiments of the present invention have been described in detail above, the present invention is not limited to these embodiments, and various modifications and changes are possible within the scope of the gist of the present invention described in the claims. [Explanation of symbols]

[0070] 100 Power conversion device 10 Inverter 20 Rotating Electric Machine 21 windings 21U U phase winding 21V V phase winding 21W W-phase winding 31 First storage unit 32 Second storage unit 31a,32a Internal resistance 41 Voltage sensor 51 Current Sensor 52 Current Sensor 60 connection routes 61 Switch 71 Smoothing capacitor 110 Control device (control unit) B Intermediate terminal CH-1, CL-1 external connection terminal im alternating current O neutral point

Claims

1. a first power storage unit and a second power storage unit that form a series connection; an inverter connected in parallel to the series-connected body; a rotating electric machine driven by a current supplied from the inverter; a connection path that electrically connects the rotating electric machine to an intermediate terminal between the first power storage unit and the second power storage unit; a control unit that controls a switching operation of the inverter to control a current flowing through the rotating electric machine and the connection path; an external connection terminal for connecting an external power source to the series-connected body; Equipped with The control unit a temperature increase mode in which a current is supplied to the intermediate terminal via the connection path to increase the temperatures of the first power storage unit and the second power storage unit; In the temperature rise mode, a command value of the AC component current to be supplied to the intermediate terminal via the connection path is calculated, the command value of the AC component current having a current waveform in which the difference between the maximum and minimum current values ​​within a fundamental wave period of the AC is smaller than the difference between the maximum and minimum values ​​of a fundamental sine wave. A power conversion device characterized by:

2. The control unit In the temperature rise mode, a command value of the current of the AC component is calculated so as to have at least odd-order harmonic components whose effective amplitude value is smaller than that of the fundamental sine wave.

2. The power conversion device according to claim 1.

3. The control unit In the temperature rise mode, a command value of the AC component current is calculated so that the transition time from near the maximum value on the positive side to near the maximum value on the negative side of the AC current flowing through the rotating electric machine and the connection path has a waveform that is shorter than the fundamental sine wave.

2. The power conversion device according to claim 1.

4. The control unit In the temperature rise mode, an output voltage of the series-connected body is detected, and when the detected output voltage of the series-connected body exceeds a predetermined voltage fluctuation tolerance range, an amplitude of an AC current flowing through the rotating electric machine and the connection path is reduced.

4. The power conversion device according to claim 1, wherein the first and second power sources are connected to each other.

5. The control unit When the external power supply is not connected to the external connection terminal, the allowable voltage fluctuation range is made larger than when the external power supply is connected to the external connection terminal.

5. The power conversion device according to claim 4.

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