Battery system

Abstract

To efficiently raise the temperature of a battery and to suppress a deterioration of an audibility when the temperature of the battery rises.SOLUTION: DC power from a battery is converted into AC power by an inverter so as to drive a motor generator (GM). A control ECU executes a temperature rise control when the temperature of the battery is low (YES in S10). In the temperature rise control, the control ECU sets the carrier frequency of the inverter to be a resonance frequency Rf of a battery circuit including the battery. The frequency of a switching ripple current becomes consistent with the resonance frequency Rf, the amplitude of a current ripple increases, and thus the temperature of the battery can be efficiently caused to rise (heating). The sound pressure level increases only in the region of the resonance frequency Rf, and thus a deterioration of an audibility can be suppressed.SELECTED DRAWING: Figure 2

Description

[Technical field]

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

[0002] US Patent Application Publication No. 2022 / 0223937 (Patent Document 1) discloses an electric vehicle equipped with a battery. In the electric vehicle of Patent Document 1, the DC power of the battery is converted to AC power by an inverter to drive a motor generator. In Patent Document 1, when the temperature of the battery is below a threshold value, the d-axis current of the motor generator is adjusted without changing the switching frequency of the inverter to generate an AC current (current ripple) in the battery and heat (raise the temperature) the battery. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] US Patent Application Publication No. 2022 / 0223937 Summary of the Invention [Problem to be solved by the invention]

[0004] In the input / output current of a battery, if the frequency of the current ripple (hereinafter also referred to as the ripple frequency) is controlled to the resonant frequency of a circuit (battery circuit) including the battery, 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 (or the current input to the inverter) to the resonant frequency of the battery circuit.

[0005] The inverter is driven at a specified switching frequency (carrier frequency). A ripple current (switching ripple current) is generated by the switching of the inverter. This ripple current flows into the battery circuit. For this reason, if the ripple frequency of the current output from the inverter is controlled to the resonant frequency of the battery circuit in order to increase the temperature (heat) of the battery, there is a concern that the sound pressure level will increase in the two frequency ranges of the switching frequency and the resonant frequency, deteriorating the sense of hearing.

[0006] An object of the present disclosure is to efficiently raise the temperature of a battery and to suppress deterioration of hearing sensation when the temperature of the battery is raised. [Means for solving the problem]

[0007] 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 switching frequency, and converting DC power stored in the battery into AC power to supply 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 to set the switching frequency to the resonant frequency of the circuit including the battery and drive the inverter when the battery is heated.

[0008] According to this configuration, the 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 switching frequency by the control device. The switching frequency is set to a resonance frequency of the circuit including the battery (battery circuit) when the temperature of the battery is raised.

[0009] When the battery is heated, the switching frequency is set to the resonant frequency, so that the frequency of the switching ripple current (the ripple current generated by the inverter switching) becomes the resonant frequency. This increases the amplitude of the battery current ripple due to resonance, and the battery can be heated efficiently. In addition, because the battery is heated using the switching ripple current, the sound pressure level increases only in the resonant frequency range, and deterioration of hearing can be suppressed.

[0010] Preferably, the battery system is mounted on a vehicle, and the control device may be configured to raise 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 temperature.

[0011] 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.

[0012] Preferably, the electric machine is a rotating electric machine, and the control device may set a d-axis current of the rotating electric machine to a predetermined value and a q-axis current of the rotating electric machine to zero when raising the temperature of the battery.

[0013] According to this configuration, when the temperature of the battery is increased, the d-axis current supplied to the rotating electric machine is set to a predetermined value, and the q-axis current is set to 0, so that the battery can be increased without torque being output from the rotating electric machine. The rotating electric machine may be a synchronous motor, for example, an IPM (Interior Permanent Magnet) synchronous motor. Effect of the Invention

[0014] 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]

[0015] [Figure 1] 1 is an overall configuration diagram of a battery system according to an embodiment of the present invention; [Diagram 2] FIG. 2 is a diagram showing a part of a block diagram of MG control configured in a control ECU. [Diagram 3] 4 is a flowchart showing an example of a battery temperature increase control executed by a control ECU. [Figure 4] 6A and 6B are diagrams illustrating a ripple current in the temperature rise control of a battery. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] 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.

[0017] 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.

[0018] 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.

[0019] 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.

[0020] The battery 30 is provided with a monitoring unit 35. The monitoring unit 35 includes sensors for detecting the voltage VB of the single cells 31, the input / output current IB of the battery 30, and the temperature TB of the battery 30, and outputs signals indicative of the detection results to the control ECU 50.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] The inverter 20 is PWM (Pulse Width Modulation) controlled by the control ECU 50 at a predetermined switching frequency to drive the MG 10. FIG. 2 is a diagram showing a part of a block diagram of the MG control configured in the control ECU 50. 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 uses the d-axis current command value id* and the d-axis current id to obtain a d-axis voltage command Vd* by PI control. The control ECU 50 also uses the q-axis current command value iq* and the q-axis current iq to obtain a q-axis voltage command Vq* by PI control.

[0027] The control ECU 50 performs dq-UVW conversion on the d-axis voltage command Vd* and the q-axis voltage command Vq* to obtain three-phase voltage commands Uv*, Vv*, and Wv*. The control signals S1 to S6 are generated by PWM control using a carrier (triangular wave) signal 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, and the inverter 20 is driven. The switching frequency of the inverter 20 varies depending on the frequency (carrier frequency) of the carrier signal, and the switching frequency has the same value as the carrier frequency. In the present disclosure, the switching frequency and the carrier frequency are synonymous. In the present embodiment, the carrier frequency (switching frequency) is made variable by the switching signal SS.

[0028] 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 from the external power source (external charging) becomes possible.

[0029] 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 heat 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 use the generated Joule heat to heat the battery 30. 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 matches 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 efficiently raised.

[0030] FIG. 3 is a flowchart showing an example of 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. In addition, if timer charging is set, it may be determined that there is a charging request 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 temperature α. The predetermined temperature α may be, for example, 0°C. If the temperature TB is equal to or lower than the predetermined temperature α, a positive determination is made and the process proceeds to S11. If the temperature TB is higher than the predetermined temperature α, the current routine is terminated.

[0031] In S11, temperature rise control is executed. The temperature rise control is MG control that controls the MG 10, and the carrier frequency of the inverter 20 is set to Rf to drive the inverter 20. Rf is the resonant frequency of the battery circuit. By setting the carrier frequency to Rf (resonant frequency), the switching frequency of the inverter 20 becomes Rf. At this time, since the vehicle V is in preparation for external charging or is being externally charged and is stopped, the q-axis current command value iq* is set to 0 (zero) and the d-axis current command value id* is set to a predetermined value a so that no torque is output from the MG 10. Note that Rf (resonant frequency) is obtained in advance by an experiment or the like and stored in the control ECU 50.

[0032] When the switching frequency of the inverter 20 is set to Rf, a switching ripple current having a frequency of Rf flows to the battery 30. The PWM control of the inverter 20 switches the switching elements Q1 to Q6 based on the switching frequency (carrier frequency), and this switching operation serves as an excitation source to generate a switching ripple current having a frequency of Rf. As a result, the frequency of the current ripple (ripple frequency) for raising the temperature of the battery 30 matches Rf (resonance frequency), and the amplitude of the current ripple increases due to resonance, increasing the amount of Joule heat generated, so that the temperature of the battery 30 can be raised efficiently.

[0033] In the next S12, it is determined whether the temperature TB of the battery 30 is equal to or higher than a predetermined temperature β. The predetermined temperature β is a value larger than the predetermined temperature α, and may be, for example, 15°C. If the temperature TB is lower than the predetermined temperature β, the temperature rise control is continued. If the temperature TB is equal to or higher than the predetermined temperature β, the process proceeds to S13, and the temperature rise control is terminated. To terminate the temperature rise control, the carrier frequency is set to Cf, and the d-axis current command value id* and the q-axis current command value iq* are set to 0, and the drive of the inverter 20 (MG10) is stopped. Note that Cf is a carrier frequency in normal operation, and may be, for example, 5000 Hz. After the temperature rise control is terminated, the current routine is terminated. Note that during the temperature rise control, the system main relay SMR is closed.

[0034] FIG. 4 is a diagram for explaining the ripple current in the temperature rise control of the battery 30. FIG. 4(A) is an example of the ripple current in this embodiment. When the temperature rise control is started in S11 (FIG. 3), the q-axis current command value iq* is set to 0, and the d-axis current command value id* is set to a predetermined value a. Then, the carrier frequency is set to Rf, and the PWM control of the inverter 20 is executed. This generates a switching ripple current having a frequency of Rf. Since Rf is the resonance frequency of the battery circuit, the ripple frequency of the input / output current IB of the battery 30 coincides with Rf (resonance frequency), and the amplitude of the current ripple of the input / output current IB becomes large due to the resonance. This increases the amount of Joule heat generated, and the temperature rise of the battery 30 is efficiently performed. The magnitude of the predetermined value a may be determined by an experiment or the like so that the amplitude of the current ripple of the input / output current IB due to the resonance becomes large enough to raise the temperature of the battery 30.

[0035] FIG. 4B is an example of a ripple current in a comparative example. In the comparative example, the carrier frequency is set to Cf. The q-axis current command value iq* is set to 0, and the d-axis current command value id* is set to a value obtained by superimposing a resonance ripple current of Rf (resonance frequency) on a predetermined value a. Current ripples in the input / output current IB of the battery 30 occur in the region of the resonance frequency (Rf) whose amplitude is increased by resonance (see the dashed line) and in the region of the carrier frequency (Cf) (see the solid line) caused by the switching ripple current, and the sound pressure level increases in the two frequency regions, deteriorating the hearing sensation. Note that the input / output current IB has a waveform in which a solid line is superimposed on a dashed line in FIG. 4B.

[0036] In contrast, in the present embodiment shown in FIG. 4(A), the current ripple of the input / output current IB occurs only in the region of the resonant frequency (Rf), so that deterioration of the hearing sensation can be suppressed.

[0037] In this embodiment, when controlling the temperature rise of the battery 30, the switching frequency (carrier frequency) of the inverter 20 is set to the resonant frequency (Rf) of the battery circuit, and the inverter 20 is driven. The ripple frequency of the input / output current IB of the battery 30 coincides with Rf (resonant frequency), and the amplitude of the current ripple of the input / output current IB increases due to resonance. This increases the amount of Joule heat generated, and the temperature rise of the battery 30 is efficiently performed. In addition, the current ripple of the input / output current IB occurs only in the region of the resonant frequency (Rf), so the hearing sensation does not deteriorate.

[0038] In the above embodiment, the temperature increase control of the battery 30 is performed when there is a request for charging. However, even if there is no request for charging, the temperature increase control may be performed when the temperature TB of the battery 30 is low. In this case, the d-axis current command value id* and the q-axis current command value iq* are set to values ​​calculated based on the output torque command value, and the carrier frequency of the inverter 20 is set to Rf. Then, when the temperature increase (heating) of the battery 30 is completed, the carrier frequency of the inverter 20 is set to Cf (returned to Cf).

[0039] 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]

[0040] 10 motor generator (MG), 20 inverter, 30 battery, 31 cell, 35 monitoring unit, 50 control ECU, 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 switching 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 battery system sets the switching frequency to the resonant frequency to drive the inverter.

2. The battery system is mounted on a vehicle, The control device includes: 2 . The battery system according to claim 1 , 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 temperature, the temperature of the battery is increased.

3. the electric machine is a rotating electric machine, When increasing the temperature of the battery, the control device 3. The battery system according to claim 2, wherein a d-axis current of the rotating electric machine is set to a predetermined value, and a q-axis current of the rotating electric machine is set to zero.

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