Battery system

Abstract

The invention provides a battery system. The battery system converts DC power of a storage battery into AC power by an inverter and drives a motor generator (MG). The control ECU executes temperature rise control when the storage battery is at a low temperature. During temperature rise control, the control ECU sets the carrier frequency of the inverter to the resonant frequency of a battery circuit including the storage battery. The frequency of the switching ripple current coincides with the resonant frequency, and the amplitude of the current ripple is increased, so that the temperature of the battery can be efficiently raised (heated). In addition, the sound pressure level is increased only in the resonant frequency region, and deterioration of hearing can be suppressed.

Description

Technical Field

[0001] The present disclosure relates to battery systems. Background Art

[0002] A battery electric vehicle equipped with a battery is disclosed in U.S. Patent Application Publication No. 2022 / 0223937. In the battery electric vehicle disclosed in U.S. Patent Application Publication No. 2022 / 0223937, the DC power of the battery is converted into AC power by an inverter to drive an electric generator. In U.S. Patent Application Publication No. 2022 / 0223937, when the temperature of the battery is less than a threshold value, the switching frequency of the inverter is not changed and the d-axis current of the electric generator is adjusted to generate an AC current (current ripple) in the battery to heat the battery (increase the temperature). Summary of the invention

[0003] In the input and output current of the storage battery (battery), when the frequency of the current ripple (hereinafter also referred to as the ripple frequency) is controlled to the resonant frequency of the circuit (battery circuit) including the storage battery (battery), the amplitude of the current ripple becomes larger due to the resonance, and the battery can be efficiently heated up. Therefore, it is considered to control 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 to efficiently heat the battery.

[0004] The inverter is driven at a predetermined switching frequency (carrier frequency). The switching of the inverter generates a ripple current (switching ripple current). This ripple current flows through the battery circuit. Therefore, 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, the sound pressure level in the two frequency regions of the switching frequency and the resonant frequency becomes large, and the hearing may be deteriorated.

[0005] An object of the present disclosure is to efficiently increase the temperature of a battery and suppress deterioration of hearing when the temperature of the battery increases.

[0006] The battery system disclosed in the present invention comprises: a battery; an electric machine; an inverter connected between the battery and the electric machine, driven at a predetermined switching frequency, and converting the DC power stored in the battery into AC power and supplying it 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 when the battery is heated, and drive the inverter.

[0007] According to this structure, the DC power stored in the battery is converted into AC power by the inverter and supplied to the electric machine. The inverter is driven at a predetermined switching frequency by the control device. When the battery is heated, the switching frequency is set to the resonant frequency of the circuit including the battery (battery circuit).

[0008] When the battery temperature rises, the switching frequency is set to the resonant frequency, so the frequency of the switching ripple current (ripple current generated by the switching of the inverter) becomes the resonant frequency. As a result, the amplitude of the battery current ripple increases through resonance, and the battery temperature can be effectively raised (heated). In addition, since the battery temperature is raised using the switching ripple current, the sound pressure level increases only in the resonant frequency region, which can suppress the deterioration of hearing.

[0009] Preferably, the battery system may be mounted on a vehicle, and 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 control device may increase the temperature of the battery.

[0010] According to this configuration, when the temperature of the battery is low during external charging of the electric vehicle (electrified vehicle), the temperature of the battery is raised, so that external charging can be performed satisfactorily.

[0011] Preferably, the electric machine may be a rotating electrical machine, and the control device may set a d-axis current of the rotating electrical machine to a predetermined value and a q-axis current of the rotating electrical machine to zero when raising the temperature of the battery.

[0012] According to this configuration, when the battery temperature is raised, the d-axis current supplied to the rotating electrical machine is set to a predetermined value and the q-axis current is set to 0, so that the battery temperature can be raised without outputting torque from the rotating electrical machine. The rotating electrical machine may be a synchronous motor, for example, an interior permanent magnet (IPM) synchronous motor.

[0013] According to the present disclosure, the battery temperature can be raised efficiently, and noise generated when the battery temperature is raised can be suppressed. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will be described below with reference to the accompanying drawings, in which like reference numerals represent like elements, wherein:

[0015] Figure 1 is an overall structural diagram of the battery system of this embodiment;

[0016] Figure 2 is a diagram showing a partial block diagram of the MG control configured in the control ECU;

[0017] Figure 3is a flowchart showing an example of battery temperature increase control executed by the control ECU;

[0018] Figure 4A is a diagram for explaining ripple current in battery temperature rise control;

[0019] Figure 4B This is a diagram for explaining another example of the ripple current in the temperature increase control of the battery. DETAILED DESCRIPTION

[0020] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In addition, the same reference numerals are given to the same or corresponding parts in the drawings, and their description will not be repeated.

[0021] Figure 1 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 a pure electric vehicle or a plug-in hybrid electric vehicle. Figure 1 The battery system 100 includes a motor generator (MG) 10, an inverter 20 as a power control unit (PCU), a battery 30, a system main relay SMR, and a control electronic control unit (ECU) 50 as a control device.

[0022] MG10 is a driving motor that generates torque for driving a driving wheel (not shown) of a vehicle V. MG10 is a rotating electrical machine, for example, an IPM synchronous motor in which a permanent magnet is embedded in a rotor. In addition, MG10 may also have a function as a generator, or may be configured to have both the function of a motor and a generator. MG10 is equivalent to an example of an "electrical machine" in the present disclosure.

[0023] The storage battery 30 is composed of a secondary battery such as a lithium-ion battery, which is equivalent to the "battery" of the present disclosure. The secondary battery can be a battery having a liquid electrolyte between the positive electrode and the negative electrode, or a battery having a solid electrolyte (all-solid-state battery). The storage battery 30 is composed of a battery pack composed of a plurality of single cells (battery units) 31 such as lithium-ion batteries electrically connected in series.

[0024] 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 these detection results to the control ECU 50 .

[0025] System main relay SMR is connected between the positive terminal of battery 30 and power line PL and between the negative terminal of battery 30 and power line NL. System main relay SMR switches between open and closed states in accordance with a control signal from control ECU 50 .

[0026] Capacitor C connected between power line PL and power line NL is provided between inverter 20 and battery 30. Capacitor C smoothes the battery voltage and supplies it to inverter 20. Voltage sensor 40 detects voltage across capacitor C, that is, voltage between power lines PL and NL connecting battery 30 and inverter 20 (hereinafter also referred to as "system voltage") VH, and outputs a signal indicating the detection result to control ECU 50.

[0027] Inverter 20 converts DC power supplied from battery 30 into AC power and supplies it to MG 10. Inverter 20 also converts AC power generated by MG 10 into DC power and supplies it to battery 30. That is, battery 30 can transfer power to and from MG 10 via inverter 20.

[0028] 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 to each other between the power line PL and the power line NL. The U-phase arm 21 has switching elements Q1 and Q2 connected in series with each other. The V-phase arm 22 has switching elements Q3 and Q4 connected in series with each other. The W-phase arm 23 has switching elements Q5 and Q6 connected in series with each other. Diodes D1 to D6 are respectively connected in anti-parallel between the collector and emitter of each switching element Q1 to Q6. The switching action of the switching elements Q1 to Q6 is performed by control signals (gate signals) S1 to S6 from the control ECU 50.

[0029] The middle point of each phase arm is connected to each phase end of each phase coil of MG10. The other ends of the three coils of U phase, V phase and W phase of MG10 are connected to the neutral point. The current sensor 60 detects the three-phase current iu, iv, iw flowing in MG10 and outputs a signal indicating the detection result to the control ECU50.

[0030] The inverter 20 is controlled by the control ECU 50 by pulse width modulation (PWM: Pulse Width Modulation) at a predetermined switching frequency to drive the MG 10 . Figure 2This is a diagram showing a partial block diagram of the MG control constituted in the control ECU 50. The software (program) and hardware of the control ECU 50 cooperate to constitute the function of the 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 the d-axis current id and the q-axis current iq. In addition, the control ECU 50 calculates the d-axis current command value id* and the q-axis current command value iq* based on the output torque command value. Then, using the d-axis current command value id* and the d-axis current id, the d-axis voltage command Vd* is obtained through PI control. In addition, using the q-axis current command value iq* and the q-axis current iq, the q-axis voltage command Vq* is obtained through PI control.

[0031] The control ECU 50 performs dq-UVW transformation 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*. In order to supply the voltages of the three-phase voltage commands Uv*, Vv*, and Wv* to the U-phase, V-phase, and W-phase of the MG 10, respectively, control signals S1 to S6 are generated by PWM control using a carrier (triangular wave) signal to drive the inverter 20. The switching frequency of the inverter 20 varies according to the frequency of the carrier signal (carrier frequency), and the switching frequency is the same value as the carrier frequency. In the present disclosure, the switching frequency is synonymous with the carrier frequency. In the present embodiment, the carrier frequency (switching frequency) can be variable according to the switching signal SS.

[0032] The vehicle V has an inlet 90, and the battery 30 is charged using power from an external power source. The inlet 90 is connected to the positive terminal and the negative terminal of the battery 30 via a charging relay CHR. When a plug 201 of an electric vehicle supply equipment (EVSE: Electric Vehicle Supply Equipment) 200 is connected to the inlet 90 and the charging relay CHR is closed, charging (external charging) based on the external power source can be performed.

[0033] When the temperature TB of the battery 30 is low, the charging and discharging performance is reduced due to an increase in the internal resistance, etc. Therefore, when the temperature TB of the battery 30 is low, it is preferable to raise the temperature of the battery 30. Consider causing a ripple current to flow through the battery 30 to generate a current ripple, and using the generated Joule heat to raise the temperature of the battery 30. The battery circuit (LC series circuit or RLC series circuit) including the battery 30, the capacitor C, etc. has a resonant frequency Rf. When the frequency (ripple frequency) of the current ripple used to raise the temperature of the battery 30 coincides with the resonant 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.

[0034] Figure 3This is a flowchart showing an example of battery temperature rise control performed 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, it can also be set that the plug 201 is connected to the insertion port 90, and there is a charging request when there is a charging instruction. In addition, when timed charging is set, it can be determined that there is a charging request before the set time from the start time of charging. When there is a charging request, the control ECU 50 determines in step (hereinafter, the step is referred to as "S") 10 whether the temperature TB of the battery 30 is below the specified temperature α. The specified temperature α can be, for example, 0[℃]. When the temperature TB is below the specified temperature α, it is determined to be affirmative and enters S11. When the temperature TB is higher than the specified temperature α, the routine ends.

[0035] In S11, temperature rise control is performed. Temperature rise control is MG control for controlling MG10, setting the carrier frequency of inverter 20 to Rf, and driving inverter 20. Rf is the resonant frequency of the battery circuit. By setting the carrier frequency to the resonant frequency (Rf), the switching frequency of inverter 20 becomes Rf. At this time, since the vehicle V is stopped in preparation for external charging or in external charging, the q-axis current command value iq* is set to 0 (zero), and the d-axis current command value id* is set to a specified value a, so that torque is not output from MG10. In addition, the resonant frequency (Rf) is obtained in advance by experiments, etc., and stored in the control ECU50.

[0036] When the switching frequency of the inverter 20 is set to Rf, a switching ripple current having a frequency of Rf flows through the battery 30. The PWM control of the inverter 20 switches the switching elements Q1 to Q6 based on the switching frequency (carrier frequency), so the switching action is used as an excitation source to generate a switching ripple current having a frequency of Rf. As a result, the frequency (ripple frequency) of the current ripple used to increase the temperature of the battery 30 is consistent with the resonance frequency (Rf), and the amplitude of the current ripple increases through resonance, and the amount of Joule heat generated increases. Therefore, the temperature of the battery 30 can be increased efficiently.

[0037] In the next S12, it is determined whether the temperature TB of the battery 30 is above the specified temperature β. The specified temperature β is a value greater than the specified temperature α, for example, it can be 15 [℃]. When the temperature TB is lower than the specified temperature β, the temperature rise control continues. When the temperature TB is above the specified temperature β, enter S13 and end the temperature rise control. The temperature rise control ends by setting the carrier frequency to Cf, and setting the d-axis current command value id* and the q-axis current command value iq* to 0, and stopping the drive of the inverter 20 (MG10). In addition, Cf is the normal carrier frequency, for example, it can be 5000 [Hz]. After the temperature rise control ends, the current routine ends. During the temperature rise control process, the system main relay SMR is closed.

[0038] Figure 4A , Figure 4B This is a diagram for explaining the ripple current in the temperature increase control of the battery 30 . Figure 4A is an example of the ripple current in this embodiment, and when S11 ( Figure 3 ), when the temperature rise control is started in the inverter 20, the q-axis current command value iq* is set to 0, and the d-axis current command value id* is set to the specified value a. Then, the carrier frequency is set to Rf, and the PWM control of the inverter 20 is performed. As a result, a switching ripple current with a frequency of Rf is generated. Rf is the resonant frequency of the battery circuit, so the ripple frequency of the input and output current IB of the battery 30 is consistent with the resonant frequency (Rf), and the amplitude of the current ripple of the input and output current IB becomes larger due to the resonance. As a result, the amount of Joule heat generated becomes larger, and the temperature rise of the battery 30 is implemented efficiently. In addition, the size of the specified value a can be determined by experiments, etc., so that the amplitude of the current ripple of the input and output current IB caused by the resonance becomes large enough to raise the temperature of the battery 30.

[0039] Figure 4B is an example of ripple current in the comparative example. In the comparative example, the carrier frequency is set to Cf. Then, 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 the resonant ripple current of the resonant frequency (Rf) on the specified value a. The current ripple of the input-output current IB of the battery 30 is generated in the area of ​​the resonant frequency (Rf) where the amplitude increases due to resonance (refer to the dotted line) and in the area of ​​the carrier frequency (Cf) caused by the switching ripple current (refer to the solid line). The sound pressure level increases in the two frequency domains, and the hearing deteriorates. In addition, the input-output current IB Figure 4B The waveform is a combination of solid and dotted lines.

[0040] In contrast, Figure 4A In the present embodiment shown, the current ripple of the input-output current IB is generated only in the region of the resonance frequency (Rf), and thus deterioration of the auditory sense can be suppressed.

[0041] 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 is consistent with the resonant frequency (Rf), and the amplitude of the current ripple of the input / output current IB increases through resonance. As a result, the amount of Joule heat generated increases, and the temperature rise of the battery 30 is efficiently implemented. In addition, the current ripple of the input / output current IB is generated only in the region of the resonant frequency (Rf), so the hearing is not deteriorated.

[0042] In the above embodiment, when there is a charge request, the temperature increase control of the battery 30 is performed. However, even when there is no charge request, the temperature increase control can 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).

[0043] The embodiments disclosed herein are illustrative in all aspects and should not be considered restrictive. The scope of the present disclosure is not indicated by the description of the embodiments described above, but by the scope of the patent claims, and is intended to include the meaning equivalent to the scope of the patent claims and all changes within the scope.

Claims

1. A battery system comprising: Battery; Electric machinery; an inverter connected between the battery and the electric machine, driven at a predetermined switching frequency, and converting the DC power stored in the battery into AC power to supply the AC power to the electric machine; and Control device, A circuit including the battery has a resonant frequency, The control device sets the switching frequency to the resonant frequency to drive the inverter when raising the temperature of the battery.

2. The battery system according to claim 1, wherein: The battery system is mounted on a vehicle. The control device increases 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.

3. The battery system according to claim 2, wherein: The electric machine is a rotating electrical machine, The control device sets a d-axis current of the rotating electrical machine to a predetermined value and sets a q-axis current of the rotating electrical machine to zero when raising the temperature of the battery.

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