Characteristics of Battery-Internal-Heating Method Involving Dq-Axis Current Pulsation in Permanent Magnet Synchronous Motors During Electric Vehicle Operation

The discharge voltage and capacity of lithium-ion batteries (LIBs), widely used in electric vehicles (EVs), decrease at sub-zero temperatures. Therefore, the temperature needs to be rapidly increased to increase the output of the drive motor. One of the methods for raising the internal temperature of LIBs is the usage of the Joule heat of LIBs. A method for raising the internal temperature during EV operation has been developed by pulsating the dq-axis current of a permanent magnet synchronous motor on an equal-torque curve and generating Joule heat in the battery via alternating current. In this study, the quantitative relationship between the frequency and amplitude of the dq-axis current pulsation and the battery current is established and the mechanism of the temperatureraising method is clarified. The effect of the heating method involving dq-axis current pulsation is also clarified quantitatively to design the drive system.