US-12620647-B2 - Battery system

Abstract

The DC power of the battery is converted into AC power by an inverter to drive a motor generator (MG). The control ECU executes the temperature raising control at the time of low temperature of the battery. During the temperature raising control, the control ECU sets the carrier frequency of the inverter to the resonance frequency of the battery circuit including the battery. The frequency of the switching ripple current coincides with the resonance frequency, and the amplitude of the current ripple increases, so that the battery can be efficiently raised in temperature (heated). The sound pressure level increases only in the region of the resonance frequency, and an increase in loudness can be reduced.

Inventors

• Hirotsugu OHATA
• Wan Leng Ang
• Shinya Asaura

Assignees

• TOYOTA JIDOSHA KABUSHIKI KAISHA

Dates

Publication Date

20260505

Application Date

20240701

Priority Date

20230928

Claims (5)

1. 1 . A battery system comprising: a battery pack that is an assembly of single cells electrically connected in series; an electrical machine; an inverter connected between the battery pack and the electrical machine, the inverter being configured to convert direct current power stored in the battery pack to alternating current power to supply the alternating current power to the electrical machine; a control device configured to drive the inverter by pulse-width modulation, and perform a warming process of increasing a temperature of the battery pack; a first relay connected between the inverter and a first terminal of the battery pack; a second relay connected between the inverter and a second terminal of the battery pack; and a capacitor connected between a first power line and a second power line, the first power line connecting the first relay and the inverter, and the second power line connecting the second relay and the inverter, wherein the first relay and the second relay are closed during the warming process, the warming process includes setting a switching frequency of the pulse-width modulation to the same frequency as a resonance frequency of a circuit that includes the battery pack and the capacitor, the battery system is mounted on a vehicle, the vehicle including a charging inlet, and the control device is configured to detect insertion of a plug of an electronic charger into the charging inlet, detect the temperature of the battery pack using a temperature sensor, determine whether the detected temperature of the battery pack is equal to or lower than a first predetermined temperature, in response to the insertion of the plug, start the warming process in response to determining that the temperature of the battery pack is equal to or lower than the first predetermined temperature, determine whether the detected temperature of the battery pack is equal to or higher than a second predetermined temperature that is larger than the first predetermined temperature, during the warming process, and end the warming process in response to determining that the detected temperature of the battery pack is equal to or higher than the second predetermined temperature.
2. 2 . The battery system according to claim 1 , wherein: the electrical machine is a rotating electrical machine; and the warming process further includes setting a d-axis current of the rotating electrical machine to a predetermined value, and setting a q-axis current of the rotating electrical machine to zero.
3. 3 . The battery system according to claim 1 , wherein: the pulse-width modulation is performed with a predetermined frequency at a time other than duration of the warming process; and the control device is configured to set the switching frequency to the predetermined frequency to end the warming process.
4. 4 . The battery system according to claim 2 , wherein the control device is configured to set the d-axis current and the q-axis current to zero to end the warming process, in response to determining that the detected temperature of the battery pack is equal to or higher than the second predetermined temperature.
5. 5 . The battery system according to claim 1 , further comprising a sensor in the circuit, the sensor being configured to detect a voltage across the capacitor.

Description

CROSS-REFERENCE TO RELATED APPLICATION This application claims priority to Japanese Patent Application No. 2023-168434 filed on Sep. 28, 2023, incorporated herein by reference in its entirety. BACKGROUND 1. Technical Field The present disclosure relates to battery systems. 2. Description of Related Art U.S. Unexamined Patent Application Publication No. 2022/0223937 discloses a battery electric vehicle equipped with a battery. In the battery electric vehicle of U.S. Unexamined Patent Application Publication No. 2022/0223937, direct current power of the battery is converted to alternating current power by an inverter to drive a motor generator. In U.S. Unexamined Patent Application Publication No. 2022/0223937, when the temperature of the battery is less than a threshold, a d-axis current of the motor generator is adjusted without changing the switching frequency of the inverter. An alternating current (current ripple) is thus generated in the battery to heat (raise the temperature of) the battery. SUMMARY When the frequency of current ripple (hereinafter also referred to as “ripple frequency”) in an input and output current of a battery is controlled to a resonance frequency of a circuit including the battery (battery circuit), the amplitude of the current ripple increases due to resonance, so that the battery can be efficiently raised in temperature (heated). Therefore, one possible way to efficiently raise the temperature of the battery is to control the ripple frequency of an output current from an inverter (or an input current to the inverter) to the resonance frequency of the battery circuit. The inverter is driven at a predetermined switching frequency (carrier frequency). A ripple current (switching ripple current) is generated by switching of the inverter. The ripple current flows through the battery circuit. Therefore, when the ripple frequency of the output current from the inverter is controlled to the resonance frequency of the battery circuit in order to raise the temperature of (heat) the battery, the sound pressure level increases in two frequency ranges, namely the switching frequency and the resonance frequency, which may increase loudness. An object of the present disclosure is to efficiently raise the temperature of a battery and reduce an increase in loudness when raising the temperature of the battery. A battery system according to the present disclosure includes: a battery; an electrical machine; an inverter connected between the battery and the electrical machine and configured to be driven at a predetermined switching frequency and to convert direct current power stored in the battery to alternating current power to supply the alternating current power to the electrical machine; and a control device. A circuit including the battery has a resonance frequency. The control device is configured to, when raising a temperature of the battery, set the switching frequency to the resonance frequency of the circuit including the battery and drive the inverter. With this configuration, the direct current power stored in the battery is converted to alternating current power by the inverter, and the alternating current power is supplied to the electrical machine. The inverter is driven at the predetermined switching frequency by the control device. When raising the temperature of the battery, the switching frequency is set to the resonance frequency of the circuit including the battery (battery circuit). When raising the temperature of the battery, the switching frequency is set to the resonance frequency. Therefore, the frequency of a switching ripple current (ripple current generated by switching of the inverter) becomes the resonance frequency. Accordingly, the amplitude of current ripple of the battery increases due to resonance, so that the battery can be efficiently raised in temperature (heated). Since the temperature of the battery is raised using the switching ripple current, the sound pressure level increases only in the region of the resonance frequency, so that an increase in loudness can be reduced. Preferably, the battery system may be 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. With this configuration, when the temperature of a battery is low at the time of external charging of an electrified vehicle, the temperature of the battery is raised, so that the external charging can be performed satisfactorily. Preferably, the electrical machine may be a rotating electrical machine, and the control device may be configured to, when raising the temperature of the battery, set a d-axis current of the rotating electrical machine to a predetermined value and set a q-axis current of the rotating electrical machine to zero. With this configuration, when raising the temperature of the batte