Battery system

Abstract

To provide a battery system for efficiently raising a battery temperature and suppressing noise during the battery temperature raising.SOLUTION: DC power of a battery is converted to AC power by an inverter to drive a motor generator (MG). A control ECU 50 performs temperature rise control when the battery is at a low temperature. During the temperature rise control, the control ECU 50 superimposes a current ripple to raise the battery temperature on a d-axis current command value id*. The frequency of the current ripple (ripple frequency) changes randomly around a resonance frequency Rf of the battery circuit including the battery. In addition, a carrier frequency of the inverter changes randomly. Thereby, a sound pressure level can be suppressed in the areas of the resonance frequency RF and the carrier frequency during the temperature rise control.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present disclosure relates to a battery system. [Background technology]

[0002] China Patent Publication No. 113206324 (Patent Document 1) discloses that a battery is heated by a high-frequency AC heating method. Patent Document 1 describes that a high-frequency AC pulse current having a frequency half the IGBT (Insulated Gate Bipolar Transistor) switching frequency generates Joule heat through the battery's internal resistance, heating the battery. Patent Document 1 also describes that the switching frequency is changed randomly to reduce the sound pressure level of harsh noise generated by the high-frequency AC current. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] China Patent Application Publication No. 113206324 Summary of the Invention [Problem to be solved by the invention]

[0004] The inverter is driven at a predetermined switching frequency (carrier frequency). In Patent Document 1, a ripple current (switching ripple current) generated by switching the inverter is used to generate a current ripple to raise the temperature of the battery.

[0005] If the frequency of the current ripple (hereinafter also referred to as the ripple frequency) is controlled to the resonant frequency of a circuit including a battery (battery circuit), the amplitude of the current ripple increases due to resonance, and the battery can be efficiently heated. Therefore, it is conceivable to efficiently heat the battery by controlling the ripple frequency of the current output from the inverter to the resonant frequency of the battery circuit.

[0006] If the ripple frequency of the current output from the inverter is controlled to the resonant frequency of the battery circuit, the sound pressure level will increase in the carrier frequency domain and the ripple frequency domain, raising concerns about the generation of noise.

[0007] An object of the present disclosure is to efficiently raise the temperature of a battery and to suppress noise generated when the temperature of the battery is raised. [Means for solving the problem]

[0008] The battery system according to the present disclosure includes a battery, an electric machine, an inverter connected between the battery and the electric machine, driven at a predetermined carrier frequency, converting DC power stored in the battery into AC power and supplying the AC power to the electric machine, and a control device. The circuit including the battery has a resonant frequency. The control device is configured such that, when the battery is heated, the frequency of a current ripple contained in a current supplied to the electric machine changes randomly around the resonant frequency, and the carrier frequency changes randomly.

[0009] According to this configuration, DC power stored in the battery is converted to AC power by the inverter and supplied to the electric machine. The inverter is driven at a predetermined carrier frequency by the control device. The control device randomly changes the frequency of a current ripple contained in a current supplied to the electric machine, centered on a resonant frequency of a circuit including the battery, to heat the battery. The control device randomly changes the carrier frequency when the temperature of the battery is being raised.

[0010] The frequency of the current ripple output from the inverter is controlled around the resonant frequency of the circuit including the battery, so the battery can be heated efficiently. Also, the ripple frequency and carrier frequency change randomly, so the sound pressure level in those frequency ranges is reduced, and noise generation can be suppressed.

[0011] Preferably, the electric machine is a rotating electric machine, and the current ripple may be a ripple in a d-axis current of the rotating electric machine.

[0012] According to this configuration, when the temperature of the battery is increased, the current ripple contained in the d-axis current supplied to the rotating electric machine is used, so that the temperature of the battery can be increased without changing the output torque of the rotating electric machine. The rotating electric machine may be a synchronous motor, for example, an IPM (Interior Permanent Magnet) synchronous motor.

[0013] Preferably, the battery system is mounted on a vehicle, and the control device may be configured to increase the temperature of the battery when there is a request for external charging of the battery and the temperature of the battery is equal to or lower than a predetermined value.

[0014] According to this configuration, if the battery temperature is low during external charging of the electric vehicle, the battery temperature is raised, so that external charging can be performed satisfactorily.

[0015] Preferably, the battery system further includes a first heat exchanger that exchanges heat with the rotating electric machine and a second heat exchanger that exchanges heat with the battery, and when heating the battery, the control device may dissipate heat received by the first heat exchanger from the second heat exchanger to heat the battery.

[0016] When the battery temperature rises, a d-axis current including a current ripple is supplied to the rotating electric machine. As a result, the rotating electric machine also generates heat. With this configuration, heat from the rotating electric machine is received by the first heat exchanger, and the received heat is dissipated to the battery through the second heat exchanger. The heat from the rotating electric machine can be used to raise the temperature of the battery, and the battery temperature can be raised efficiently. Effect of the Invention

[0017] According to the present disclosure, the temperature of the battery can be increased efficiently, and noise generated during the temperature increase of the battery can be suppressed. [Brief description of the drawings]

[0018] [Figure 1] 1 is an overall configuration diagram of a battery system according to an embodiment of the present invention; [Diagram 2] 13(A) and 13(B) are diagrams illustrating sound pressure levels when the temperature of a battery is rising. [Diagram 3] 4 is a flowchart of a battery temperature increase control executed by a control ECU. [Figure 4] FIG. 2 is a diagram showing a part of a block diagram of MG control in the present embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are designated by the same reference characters and their description will not be repeated.

[0020] Fig. 1 is an overall configuration diagram of a battery system 100 according to the present embodiment. The battery system 100 according to the present embodiment is mounted on, for example, a vehicle V. The vehicle V may be an electric vehicle or a plug-in hybrid vehicle. Referring to Fig. 1, the battery system 100 includes a motor generator (MG) 10, an inverter 20 serving as a power control device (PCU: Power Control Unit), a battery 30, a system main relay SMR, and a control ECU (Electronic Control Unit) 50 serving as a control device.

[0021] MG10 is a drive motor that generates torque for driving drive wheels (not shown) of vehicle V. MG10 is a rotating electric machine, for example an IPM synchronous motor with a permanent magnet embedded in the rotor. MG10 may further include a generator function, or may be configured to have both the functions of a motor and a generator. MG10 corresponds to an example of an "electric machine" in the present disclosure.

[0022] The battery 30 is configured by a secondary battery such as a lithium ion battery, and corresponds to the "battery" in this disclosure. The secondary battery may be a battery having a liquid electrolyte between the positive electrode and the negative electrode, or may be a battery having a solid electrolyte (all-solid-state battery). The battery 30 is configured as a battery pack in which a plurality of single cells (battery cells) 31 such as lithium ion batteries are electrically connected in series.

[0023] The battery 30 is provided with a monitoring unit 35. The monitoring unit 35 includes sensors for detecting the voltage VB of the cell 31, the input / output current IB of the battery 30, and the temperature TB of the battery 30, and outputs signals indicating the detection results to the control ECU 50. In this embodiment, the monitoring unit 35 detects the voltage VB of the cell 31, but is not limited to this. For example, when the cells 31 constituting the battery 30 (battery pack) are divided into a plurality of battery blocks, the voltage of each battery block may be detected. Also, the entire voltage of the battery 30 (battery pack) may be detected.

[0024] The system main relay SMR is connected between the positive terminal of the battery 30 and the power line PL, and between the negative terminal of the battery 30 and the power line NL. The system main relay SMR is switched between an open state and an closed state by a control signal from the control ECU 50.

[0025] A capacitor C connected between the power lines PL and NL is provided between the inverter 20 and the battery 30. The capacitor C smoothes the battery voltage and supplies it to the inverter 20. A voltage sensor 40 detects the voltage across the capacitor C, i.e., the voltage VH between the power lines PL and NL connecting the battery 30 and the inverter 20 (hereinafter also referred to as “system voltage”), and outputs a signal indicating the detection result to the control ECU 50.

[0026] The inverter 20 converts DC power supplied from the battery 30 into AC power and supplies it to the MG 10. The inverter 20 also converts AC power generated by the MG 10 into DC power and supplies it to the battery 30. That is, the battery 30 can exchange power with the MG 10 via the inverter 20.

[0027] The inverter 20 includes a U-phase arm 21, a V-phase arm 22, and a W-phase arm 23. The phase arms are connected in parallel between the power lines PL and NL. The U-phase arm 21 has switching elements Q1 and Q2 connected in series. The V-phase arm 22 has switching elements Q3 and Q4 connected in series. The W-phase arm 23 has switching elements Q5 and Q6 connected in series. Diodes D1 to D6 are connected in anti-parallel between the collector and emitter of each of the switching elements Q1 to Q6. The switching operations of the switching elements Q1 to Q6 are performed by control signals (gate signals) S1 to S6 from the control ECU 50.

[0028] The midpoint of each phase arm is connected to the corresponding phase end of the corresponding phase coil of MG 10. The other ends of the three coils of U-phase, V-phase, and W-phase of MG 10 are commonly connected to a neutral point. Current sensor 60 detects three-phase currents iu, iv, and iw flowing through MG 10, and outputs a signal indicative of the detection result to control ECU 50.

[0029] The vehicle V is equipped with an inlet 90, and the battery 30 is charged using power from an external power source. The inlet 90 is connected to a positive terminal and a negative terminal of the battery 30 via a charging relay CHR. When a plug 201 of a charging facility (EVSE: Electric Vehicle Supply Equipment) 200 is connected to the inlet 90 and the charging relay CHR is closed, charging by the external power source (external charging) becomes possible.

[0030] When the temperature TB of the battery 30 is low, the charging and discharging performance is reduced due to an increase in internal resistance, etc. For this reason, it is desirable to raise the temperature of the battery 30 when the temperature TB of the battery 30 is low. It is conceivable to pass a ripple current through the battery 30 to generate a current ripple, and to raise the temperature of the battery 30 by using the generated Joule heat. The inverter 20 is PWM (Pulse Width Modulation) controlled at a predetermined carrier frequency by the control ECU 50. When the MG 10 is rotationally driven, the MG 10 is sinusoidally driven by the inverter 20, and the current (MG current) supplied from the inverter 20 to the MG 10 becomes a sinusoidal wave. By superimposing a current ripple for raising the temperature of the battery 30 on this MG current, a ripple current for raising the temperature can be passed through the battery 30.

[0031] A battery circuit (LC series circuit or RLC series circuit) consisting of the battery 30 and the capacitor C, etc., has a resonance frequency Rf. When the frequency of the current ripple (ripple frequency) for heating the battery 30 coincides with the resonance frequency Rf, the amplitude of the current ripple increases due to resonance, and the amount of Joule heat generated increases, so that the temperature of the battery 30 can be raised efficiently.

[0032] In the PWM control of the inverter 20, the switching elements Q1 to Q6 are switched at the carrier frequency Cf, and this switching operation acts as an excitation source to generate a switching ripple current of the carrier frequency Cf. Therefore, when the ripple frequency is controlled to the resonant frequency Rf, the sound pressure level increases in the resonant frequency Rf region and the carrier frequency Cf region.

[0033] The upper part of Fig. 1 shows the current IB of the battery 30, the duty of the PWM control, and the MG current, and when the ripple frequency coincides with the resonance frequency Rf, the amplitude of the current IB becomes large. Note that a small amplitude corresponding to the carrier frequency Cf is superimposed on the current IB and the MG current, but this amplitude is not shown.

[0034] Fig. 2 is a diagram for explaining the sound pressure level when the temperature of the battery 30 is rising. When the resonance frequency Rf is superimposed on the MG current to raise the temperature of the battery 30, the sound pressure level becomes high in the region of the resonance frequency Rf and the carrier frequency Cf, as shown in Fig. 2(A). In Fig. 2, the dashed line indicates the sound pressure level that is acceptable in terms of noise and audibility. In this embodiment, the ripple frequency and the carrier frequency are randomly changed when the temperature of the battery 30 is rising, thereby lowering the sound pressure level in the region of the resonance frequency Rf and the carrier frequency Cf.

[0035] FIG. 3 is a flowchart of the battery temperature rise control executed by the control ECU 50. This flowchart is executed when there is a request for external charging of the battery 30 (charging request). For example, the charging request may be made when the plug 201 is connected to the inlet 90 and a charging instruction is issued. If timer charging is set, it may be determined that a charging request has been made when the set time has elapsed from the charging start time. When there is a charging request, the control ECU 50 determines in step (hereinafter, step is abbreviated as "S") 10 whether the temperature TB of the battery 30 is equal to or lower than a predetermined value α. The predetermined value α may be, for example, 0°C. If the temperature TB is equal to or lower than the predetermined value α, a positive determination is made and the process proceeds to S11. If the temperature TB is higher than the predetermined value α, the current routine is terminated.

[0036] In S11, the temperature rise control is executed. The temperature rise control is MG control that controls the MG, and controls the inverter 20 so that the frequency of the current ripple (ripple frequency) included in the MG current changes randomly around the resonance frequency Rf of the battery circuit, and the carrier frequency Cf changes randomly.

[0037] 4 is a diagram showing a part of a block diagram of MG control in this embodiment. The software (program) and hardware of the control ECU 50 cooperate to configure the function of this block diagram. The control ECU 50 performs UVW-dq conversion on the three-phase currents iu, iv, and iw detected by the current sensor 60 to obtain a d-axis current id and a q-axis current iq. The control ECU 50 also calculates a d-axis current command value id* and a q-axis current command value iq* based on the output torque command value. Then, the control ECU 50 obtains a d-axis voltage command Vd* by PI control using the d-axis current command value id* and the d-axis current id, and obtains a q-axis voltage command Vq* by PI control using the q-axis current command value iq* and the q-axis current iq.

[0038] The control ECU 50 performs dq-UVW conversion on the d-axis voltage command Vd* and the q-axis voltage command Vq* to obtain the three-phase voltage commands Uv*, Vv*, and Wv*. The control signals S1 to S6 are generated by PWM control using the carrier frequency Cf, and the inverter 20 is driven so that the voltages of the three-phase voltage commands Uv*, Vv*, and Wv* are supplied to the U-phase, V-phase, and W-phase of the MG 10, respectively.

[0039] The temperature increase control in S11 is performed when charging is requested, and is therefore performed when the MG 10 is stopped. Therefore, the q-axis current command value iq* of the MG 10 is set to 0. A current ripple for increasing the temperature of the battery 30 is superimposed on the d-axis current command value id*, and the d-axis current command value id* becomes a waveform of a ripple current flowing through the battery 30. As shown in the upper part of FIG. 4, the ripple frequency of the d-axis current command value id* is controlled to change randomly around the resonance frequency Rf of the battery circuit. The change width of the ripple frequency is arbitrary, and may be, for example, in the range of ±3 to 20% of the resonance frequency Rf. For example, when the resonance frequency Rf is 1300 [Hz], it may be changed randomly within the range of ±150 [Hz]. The method for randomly changing the ripple frequency may be arbitrary, and may be, for example, a RAND function or a RANDBETWEEN function.

[0040] In the temperature rise control, the carrier frequency Cf of the PWM control is also controlled to change randomly. The change width of the carrier frequency is arbitrary and may be within a range of ±1 to 10% of the carrier frequency Cf. For example, when the carrier frequency Cf is 4500 [Hz], it may be changed randomly within a range of ±150 [Hz].

[0041] Returning to FIG. 3, in the next S12, it is determined whether the temperature TB of the battery 30 is equal to or higher than a predetermined value β. The predetermined value β is a value larger than the predetermined value α, and may be, for example, 15° C. If the temperature TB is lower than the predetermined value β, the temperature rise control is continued. If the temperature TB is equal to or higher than the predetermined value β, the process proceeds to S13, where the drive of the inverter 20 is stopped, the MG current is set to 0, the temperature rise control is ended, and the current routine is ended. During the temperature rise control, the system main relay SMR is closed.

[0042] In this embodiment, during the temperature increase control of the battery 30, the ripple frequency of the d-axis current command value id* is controlled to change randomly around the resonance frequency Rf of the battery circuit. As a result, the ripple frequency of the MG current changes randomly around the resonance frequency Rf of the battery circuit, so the current flowing through the battery 30 also changes randomly around the resonance frequency Rf of the battery circuit. Therefore, the amplitude of the ripple current flowing through the battery 30 increases, and the battery 30 can be efficiently increased in temperature (heated). In addition, the random change in the ripple frequency and carrier frequency reduces the sound pressure level in the region of the resonance frequency Rf and the carrier frequency Cf. As shown in FIG. 2(A), the sound pressure level was high in the region of the resonance frequency Rf and the carrier frequency Cf due to the ripple current and the switching ripple current. By randomly changing the ripple frequency and the carrier frequency, the sound pressure level in the region of the resonance frequency Rf and the carrier frequency Cf decreases, as shown in FIG. 2(B).

[0043] (Modification) In the above embodiment, the MG 10 also generates heat because an MG current (d-axis current) flows through the MG 10 during temperature increase control of the battery 30. In a modified example, the heat generated by the MG 10 during temperature increase control is also used to increase the temperature of the battery 30.

[0044] In the modified example, as shown in Fig. 1, a heating circuit 80 is added. The heating circuit 80 includes a first heat exchanger 81 that exchanges heat with the MG 10, a second heat exchanger 82 that exchanges heat with the battery 30, a flow path 83 through which the heat medium flows, and a pump 84 that circulates the heat medium. When the temperature MT of the MG 10 detected by the MG temperature sensor 85 is higher than the temperature TB during the heating control of the battery 30 (after a positive determination is made in S10), the control ECU 50 drives the pump 84 to circulate the heat medium in the flow path 83. As a result, the heat of the MG 10 received by the first heat exchanger 81 is dissipated from the second heat exchanger 82 to the battery 30, thereby heating (heating) the battery 30.

[0045] In this modification, when temperature MT is higher than temperature TB, pump 84 is driven to circulate the heat medium in flow path 83. If a heat pump structure in which a compressor and an expansion valve are provided in flow path 83 is adopted as heating circuit 80, it is possible to pump out heat from MG 10 by the heat pump and heat battery 30 even when temperature MT is lower than temperature TB.

[0046] In the above embodiment, the temperature increase control of the battery 30 is performed when there is a charging request. However, even if there is no charging request, the temperature increase control may be executed when the temperature TB of the battery 30 is low. In this case, the d-axis current command value id* to be input to the PI controller is generated by superimposing a current ripple for increasing the temperature of the battery 30 on the d-axis current command value id* calculated based on the output torque command value. At this time, the frequency of the current ripple (ripple frequency) is controlled to change randomly around the resonance frequency Rf, and the carrier frequency Cf is also controlled to change randomly.

[0047] The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present disclosure is defined by the claims, not by the description of the embodiments described above, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0048] 10 motor generator (MG), 20 inverter, 30 battery, 31 battery cell, 35 monitoring unit, 50 control ECU, 80 heating circuit, 81 first heat exchanger, 82 second heat exchanger, 90 inlet, 100 battery system, 201 plug, 200 EVSE, C capacitor, V vehicle.

Claims

1. Batteries and Electrical machinery and an inverter connected between the battery and the electric machine, driven at a predetermined carrier frequency, and converting DC power stored in the battery into AC power and supplying the AC power to the electric machine; A control device, the circuit including the battery has a resonant frequency; When increasing the temperature of the battery, the control device The frequency of a current ripple contained in the AC current supplied to the electric machine varies randomly around the resonant frequency, A battery system that controls the inverter so that the carrier frequency varies randomly.

2. the electric machine is a rotating electric machine, The battery system according to claim 1 , wherein the current ripple is a ripple in a d-axis current of the rotating electric machine.

3. The battery system is mounted on a vehicle, The control device includes: 3 . The battery system according to claim 2 , wherein when there is a request for external charging of the battery and the temperature of the battery is equal to or lower than a predetermined value, the temperature of the battery is increased.

4. a first heat exchanger for exchanging heat with the rotating electric machine; A second heat exchanger that exchanges heat with the battery, When increasing the temperature of the battery, the control device The battery system according to claim 3 , wherein heat received by the first heat exchanger is dissipated from the second heat exchanger to raise the temperature of the battery.

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