Efficiency Improvement Through Dynamic Torque Modulation Motor Control in Electric Vehicle

This paper evaluates the loss reduction performance of a motor control technique called dynamic torque modulation (DTM) on motor designs with different machine loss characteristics. During low-torque operation, DTM produces a motor torque that is intermittently controlled between the torque at the motor's best-efficiency operating point and a lower value (possibly zero) to reduce drive unit (DU) loss for a given mechanical output. The electric drive unit losses are compared by applying conventional motor control (CMC) and two DTM algorithms, with inverter active at 0 torque command and deactivated at 0 torque command, to different motor designs. It is found that the benefit of DTM is highly dependent on the difference in efficiency between the best-efficiency operating line of the motor and operating points below that line. This work also demonstrates the response of a high voltage (HV) battery in an electric vehicle (EV) propulsion system under DTM control in order to determine the DTM application settings without affecting the battery behavior.