Battery system

Abstract

The invention relates to a battery system. The direct current of the battery is converted into alternating current by the inverter to drive the motor generator. When the temperature of the battery is low, the ECU is controlled to execute temperature rise control. During temperature rise control, the control ECU superimposes a current ripple for temperature rise of the battery on the d-axis current command value. A frequency (ripple frequency) of the current ripple varies randomly about a resonant frequency (Rf) of a battery circuit including a battery. In addition, the carrier frequency of the inverter varies randomly. This makes it possible to suppress the sound pressure level in the region of the resonance frequency and the carrier frequency during temperature rise control.

Description

Technical Field

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

[0002] Chinese Patent Application Publication No. 113206324 discloses a method for heating batteries using high-frequency alternating current. This technology employs a high-frequency alternating current pulse with a frequency half the switching frequency of an IGBT (Insulated Gate Bipolar Transistor) that generates Joule heat through the battery's internal resistance, heating the battery. This patent application describes randomly varying the switching frequency to reduce the harsh noise generated by the high-frequency alternating current.

[0003] The inverter is driven at a predetermined switching frequency (carrier frequency). In Chinese Patent Application Publication No. 113206324, a ripple current (switching ripple current) generated by switching of the inverter is used to generate a current ripple, thereby increasing the battery temperature.

[0004] When the frequency of the current ripple (hereinafter also referred to as the ripple frequency) is controlled to the resonant frequency of the circuit including the battery (battery circuit), the amplitude of the current ripple increases due to resonance, which can effectively increase the battery temperature (heat the battery). Therefore, it is considered to control the ripple frequency of the current output from the inverter to the resonant frequency of the battery circuit to effectively increase the battery temperature.

[0005] When the ripple frequency of the current output from the inverter is controlled to the resonant frequency of the battery circuit, the sound pressure level in the carrier frequency region and the ripple frequency region becomes large, and there is a concern that noise may be generated. Summary of the Invention

[0006] An object of the present disclosure is to efficiently increase the temperature of a battery and suppress noise during the temperature increase of the battery.

[0007] The battery system disclosed herein comprises: a battery; an electric machine; an inverter connected between the battery and the electric machine, the inverter being driven at a predetermined carrier frequency to convert direct current stored in the battery into alternating current and supply it 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 temperature is raised, the frequency of the current ripple included in the current supplied to the electric machine randomly varies around the resonant frequency, and the carrier frequency also randomly varies.

[0008] With 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 by a control device at a predetermined carrier frequency. The control device randomly varies the frequency of the current ripple contained in the current supplied to the electric machine, centered around the resonant frequency of the circuit including the battery, thereby increasing the battery temperature. As the battery temperature increases, the control device randomly varies the carrier frequency.

[0009] The frequency of the current ripple output from the inverter is controlled to center around the resonant frequency of the circuit including the battery, effectively increasing the battery temperature. Furthermore, the ripple and carrier frequencies vary randomly, reducing the sound pressure level in their frequency domains and suppressing noise generation.

[0010] Preferably, the electric machine may be a rotating electrical machine, and the current ripple may be a ripple of a d-axis current of the rotating electrical machine.

[0011] This configuration utilizes the current ripple contained in the d-axis current supplied to the rotating electrical machine when raising the battery temperature, thereby enabling the battery temperature to be raised without changing the output torque of the rotating electrical machine. The rotating electrical machine may be a synchronous motor, such as an IPM (Interior Permanent Magnet) synchronous motor.

[0012] Preferably, the battery system may be mounted on a vehicle, and the control device may 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.

[0013] According to this configuration, during external charging of the electric vehicle, the battery temperature is increased when the battery temperature is low, so that external charging can be performed satisfactorily.

[0014] Preferably, the battery system may further include: a first heat exchanger for performing heat exchange with the rotating motor; and a second heat exchanger for performing heat exchange with the battery. When heating the battery, the control device dissipates the heat received in the first heat exchanger through the second heat exchanger, thereby heating the battery.

[0015] When the battery temperature rises, a d-axis current containing current ripple is supplied to the rotating electrical machine. Consequently, the rotating electrical machine also generates heat. With this configuration, the first heat exchanger receives heat from the rotating electrical machine and dissipates this heat to the battery via the second heat exchanger. This allows the heat from the rotating electrical machine to be used to increase the battery temperature, resulting in efficient battery heating.

[0016] According to the present disclosure, the battery temperature can be increased efficiently, and noise generated during the battery temperature increase can be suppressed. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Hereinafter, features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will be described with reference to the accompanying drawings, wherein like reference numerals denote like elements, and wherein:

[0018] Figure 1 This is a diagram showing the overall configuration of the battery system according to this embodiment.

[0019] Figure 2A This is a diagram illustrating the sound pressure level when the battery temperature rises.

[0020] Figure 2B This is a diagram illustrating the sound pressure level when the battery temperature rises.

[0021] Figure 3 This is a flow chart of the battery temperature rise control executed by the control ECU.

[0022] Figure 4 This is a diagram showing a portion of a block diagram of MG control in this embodiment. DETAILED DESCRIPTION

[0023] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. It should be noted that the same or corresponding parts in the drawings are denoted by the same reference numerals, and their description will not be repeated.

[0024] Figure 1 1 is an overall configuration diagram of a battery system 100 according to this embodiment. The battery system 100 according to this embodiment is mounted on a vehicle V, for example. The vehicle V may be an electric vehicle or a plug-in hybrid 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 an electronic control unit (ECU) 50 as a control unit.

[0025] MG10 is a drive motor that generates torque for driving the drive wheels (not shown) of vehicle V. MG10 is a rotating electrical machine, for example, an IPM synchronous motor with permanent magnets embedded in the rotor. MG10 may also function as a generator, or may be configured to have both motor and generator functions. MG10 is an example of an "electrical machine" as used herein.

[0026] The battery 30 is composed of a secondary battery such as a lithium-ion battery and corresponds to the "battery" in this disclosure. A secondary battery can be a battery with a liquid electrolyte between the positive and negative electrodes, or a battery with a solid electrolyte between the positive and negative electrodes (an all-solid-state battery). The battery 30 is configured as a battery pack consisting of multiple single cells (battery units) 31, such as lithium-ion batteries, electrically connected in series.

[0027] The battery 30 is provided with a monitoring unit 35. The monitoring unit 35 includes sensors that detect the voltage VB of the battery cells 31, the input and output currents IB of the battery 30, and the temperature TB of the battery 30. The monitoring unit 35 outputs signals indicating these detection results to the control ECU 50. In this embodiment, the monitoring unit 35 detects the voltage VB of the battery cells 31, but the present invention is not limited to this. For example, if the plurality of battery 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. Alternatively, the voltage of the entire battery 30 (battery pack) may be detected.

[0028] 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 response to a control signal from control ECU 50 .

[0029] A capacitor C is provided between inverter 20 and battery 30 and connected between power line PL and power line NL. Capacitor C smoothes the battery voltage and supplies it to inverter 20. Voltage sensor 40 detects the voltage VH across capacitor C, specifically the voltage VH between power line PL and power line NL connecting battery 30 and inverter 20 (hereinafter also referred to as "system voltage"), and outputs a signal indicating the detection result of voltage VH to control ECU 50.

[0030] Inverter 20 converts DC power supplied from battery 30 into AC power and supplies it to MG 10. In addition, inverter 20 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.

[0031] 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 power line PL and power line NL. U-phase arm 21 has a switching element Q1 and a switching element Q2 connected in series with each other. V-phase arm 22 has a switching element Q3 and a switching element Q4 connected in series with each other. W-phase arm 23 has a switching element Q5 and a switching element Q6 connected in series with each other. Between the collector and emitter of each switching element Q1 to Q6, diodes D1 to D6 are respectively connected in reverse parallel to the switching elements Q1 to Q6. The switching operation of switching elements Q1 to Q6 is performed based on control signals (gate signals) S1 to S6 from control ECU 50.

[0032] The midpoint of each phase arm is connected to the respective ends of the respective phase coils of MG 10. The other ends of the three coils of MG 10 (U, V, and W phases) are connected to a common neutral point. Current sensor 60 detects the three-phase currents iu, iv, and iw flowing through MG 10 and outputs signals indicating the detection results of the three-phase currents iu, iv, and iw to control ECU 50.

[0033] Vehicle V has an inlet 90 , and battery 30 is charged using power from an external power source. Inlet 90 is connected to the positive and negative terminals of battery 30 via a charging relay (CHR). When a plug 201 of a charging device (EVSE: Electric Vehicle Supply Equipment) 200 is connected to inlet 90 and the charging relay (CHR) is closed, charging with the external power source (external charging) becomes possible.

[0034] When the temperature TB of the battery 30 is low, the charge and discharge performance will be reduced due to an increase in internal resistance, etc. Therefore, it is ideal to heat the battery 30 when the temperature TB of the battery 30 is low. Consider allowing a ripple current to flow to the battery 30 to generate current ripple, and using the generated Joule heat to heat the battery 30. The inverter 20 is controlled by the control ECU 50 using PWM (Pulse Width Modulation) at a specified carrier frequency. When the MG10 is driven to rotate, the MG10 is driven by the inverter 20 in a sinusoidal manner, and the waveform of the current (MG current) supplied from the inverter 20 to the MG10 becomes a sinusoidal wave. By superimposing the current ripple for heating the battery 30 on the MG current, the ripple current for heating can be made to flow to the battery 30.

[0035] The battery circuit (LC series circuit or RLC series circuit) composed of battery 30 and capacitor C, etc., has a resonant frequency Rf. When the frequency of the current ripple used to heat battery 30 (ripple frequency) matches the resonant frequency Rf, the amplitude of the current ripple increases due to resonance, and the amount of Joule heat generated increases, thereby efficiently heating battery 30.

[0036] During PWM control of inverter 20, switching elements Q1-Q6 are switched at carrier frequency Cf. This switching action serves as an excitation source, generating switching ripple current at carrier frequency Cf. Consequently, when the ripple frequency is controlled to resonant frequency Rf, the sound pressure level increases in the region of resonant frequency Rf and the region of carrier frequency Cf.

[0037] exist Figure 1 The upper portion of the diagram shows battery current IB, the PWM control duty cycle, and MG current. When the ripple frequency matches resonant frequency Rf, the amplitude of current IB increases. It should be noted that a small amplitude corresponding to carrier frequency Cf is superimposed on current IB and MG current, but this amplitude is not shown.

[0038] Figure 2A 、 Figure 2B This is a diagram illustrating the sound pressure level when the temperature of the battery 30 is increased. When the resonant frequency Rf is superimposed on the MG current in order to increase the temperature of the battery 30, as shown in FIG. Figure 2A As shown in FIG, the sound pressure level becomes larger in the region of the resonant frequency Rf and the carrier frequency Cf. Figure 2A 、 Figure 2B In the figure, the dashed line represents the sound pressure level acceptable to the sense of hearing based on noise. In this embodiment, the ripple frequency and carrier frequency are randomly changed when the temperature of the battery 30 rises, thereby reducing the sound pressure level in the region of the resonant frequency Rf and the carrier frequency Cf.

[0039] Figure 3 This 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, it can be set that there is a charging request when the plug 201 is connected to the inlet 90 and there is a charging instruction. In addition, it can also be that when timed charging is set, it is determined that there is a charging request when it becomes earlier than the set time when charging starts. When there is a charging request, the control ECU 50 determines whether the temperature TB of the battery 30 is less than or equal to the specified value α in step (hereinafter, the step is omitted as "S") 10. The specified value α can be 0 [℃], for example. When the temperature TB is less than or equal to the specified value α, an affirmative judgment is made and the process goes to S11. When the temperature TB is higher than the specified value α, the routine ends.

[0040] In S11, temperature increase control is executed. Temperature increase control is MG control that controls the MG. In temperature increase control, the inverter 20 is controlled so that the frequency of the current ripple (ripple frequency) included in the MG current randomly changes around the resonant frequency Rf of the battery circuit and the carrier frequency Cf randomly changes.

[0041] Figure 4 This is a diagram showing a portion of the block diagram of the MG control in this embodiment. The software (program) and hardware of the control ECU 50 cooperate to form the functions 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, the d-axis current command value id* and the d-axis current id are used to obtain the d-axis voltage command Vd* through PI (proportional-integral) control, and the q-axis current command value iq* and the q-axis current iq are used to obtain the q-axis voltage command Vq* through PI control.

[0042] Control ECU 50 performs a dq-UVW conversion on the d-axis voltage command Vd* and the q-axis voltage command Vq* to obtain three-phase voltage commands Vu*, Vv*, and Vw*. Control signals S1 to S6 are generated using PWM control using a carrier frequency Cf to drive inverter 20 so that the voltages corresponding to the three-phase voltage commands Uv*, Vv*, and Wv* are supplied to the U-phase, V-phase, and W-phase of MG 10, respectively.

[0043] The temperature increase control in S11 is performed when charging is requested, and is therefore executed when MG10 is stopped. Therefore, the q-axis current command value iq* of MG10 is set to 0. The current ripple for increasing the temperature of battery 30 is superimposed on the d-axis current command value id*, and the waveform of the d-axis current command value id* becomes the waveform of the ripple current flowing in battery 30. Figure 4 As shown in the upper section, the ripple frequency of the d-axis current command value id* is controlled to randomly vary around the resonant frequency Rf of the battery circuit. The ripple frequency can vary within any range, for example, within a range of ±3% to ±20% of the resonant frequency Rf. For example, when the resonant frequency Rf is 1300 [Hz], the ripple frequency can be randomly varied within a range of ±150 [Hz]. Any method for randomly varying the ripple frequency can be used, for example, using the RAND function or the RANDBETWEEN function.

[0044] Furthermore, during temperature increase control, the carrier frequency Cf of the PWM control is also controlled to vary randomly. The carrier frequency variation range is arbitrary, for example, within a range of ±1% to ±10% of the carrier frequency Cf. For example, when the carrier frequency Cf is 4500 [Hz], the carrier frequency Cf can be randomly varied within a range of ±150 [Hz].

[0045] return Figure 3 In the following S12, it is determined whether the temperature TB of the battery 30 is greater than or equal to the specified value β. The specified value β is a value greater than the specified value α, for example, it can be 15 [°C]. If the temperature TB is lower than the specified value β, the temperature increase control is continued. When the temperature TB is greater than or equal to the specified value β, the process proceeds to S13, stops driving the inverter 20, sets the MG current to 0, and ends the temperature increase control. It should be noted that during the temperature increase control, the system main relay SMR is closed.

[0046] In this embodiment, when controlling the temperature rise of the battery 30, the ripple frequency of the d-axis current command value id* is controlled to randomly change around the resonant frequency Rf of the battery circuit. As a result, the ripple frequency of the MG current randomly changes around the resonant frequency Rf of the battery circuit, and therefore the current flowing in the battery 30 also randomly changes around the resonant frequency Rf of the battery circuit. Therefore, the amplitude of the ripple current flowing in the battery 30 becomes larger, thereby efficiently heating the battery 30 (heating the battery 30). In addition, the ripple frequency and the carrier frequency change randomly, thereby reducing the sound pressure level in the region of the resonant frequency Rf and the carrier frequency Cf. Figure 2A As shown in Figure 1, the sound pressure level increases in the region of the resonant 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, as shown in Figure 1, the sound pressure level increases in the region of the resonant frequency Rf and the carrier frequency Cf. Figure 2B As shown, the sound pressure level in the region of the resonance frequency Rf and the carrier frequency Cf decreases.

[0047] (Variation)

[0048] In the above embodiment, during temperature increase control of battery 30, MG current (d-axis current) flows to MG 10, so MG 10 also generates heat. In a modified example, during temperature increase control, the temperature of battery 30 is increased by utilizing heat generated by MG 10.

[0049] In a modified example, Figure 1As shown, a temperature increase circuit 80 is added. Temperature increase circuit 80 includes a first heat exchanger 81 for exchanging heat with MG 10; a second heat exchanger 82 for exchanging heat with battery 30; a flow path 83 for flowing a heat medium; and a pump 84 for circulating the heat medium. During battery 30 temperature increase control (after a positive determination in S10), if MG 10 temperature MT detected by MG temperature sensor 85 is higher than temperature TB, control ECU 50 drives pump 84 to circulate the heat medium in flow path 83. This allows heat from MG 10 received in first heat exchanger 81 to be dissipated from second heat exchanger 82 to battery 30, thereby heating battery 30 (raising its temperature).

[0050] In this modified example, 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 with a compressor and an expansion valve provided in flow path 83 is employed as temperature increasing circuit 80, even when temperature MT is lower than temperature TB, the heat pump can extract heat from MG 10 to heat battery 30.

[0051] In the above embodiment, battery 30 temperature increase control is performed when a charge request is received. However, temperature increase control may also be performed when battery 30 temperature TB is low even when no charge request is received. In this case, the current ripple used to increase the battery 30 temperature is superimposed on the d-axis current command value id* calculated based on the output torque command value to generate the d-axis current command value id* input to the PI controller. In this case, the frequency of the current ripple (ripple frequency) is controlled to randomly vary around the resonant frequency Rf. Furthermore, the carrier frequency Cf is also controlled to randomly vary.

[0052] The embodiments disclosed herein are to be considered in all respects as illustrative and non-restrictive. The scope of the present disclosure is indicated not by the above description of the embodiments but by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims.

Claims

1. A battery system comprising: Battery; Electric machinery; an inverter connected between the battery and the electric machine, the inverter being driven at a predetermined carrier frequency and converting direct current stored in the battery into alternating current and supplying the alternating current to the electric machine; as well as Control device, A circuit including the battery has a resonant frequency, When the control device heats up the battery, the control device controls the inverter in the following manner: The frequency of the current ripple included in the alternating current supplied to the electric machine changes randomly around the resonance frequency, and the carrier frequency changes randomly.

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

3. The battery system according to claim 2, wherein: The battery system is mounted on a vehicle. The control device raises 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 prescribed value.

4. The battery system according to claim 3, further comprising: a first heat exchanger for performing heat exchange with the rotating electrical machine; and a second heat exchanger, performing heat exchange with the battery, When raising the temperature of the battery, the control device dissipates heat received by the first heat exchanger through the second heat exchanger to raise the temperature of the battery.

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