Suppression of Torque Ripple on MTPA Operation of IPMSM with Voltage Feedforwarding Control

Abstract

Interior permanent-magnet synchronous motor (IPMSM) has been used as the traction motor because of its higher torque density and higher efficiency. Maximum torque per ampere (MTPA) control that minimizes motor copper loss is widely applied to enhance the efficiency of IPMSM drive. However, the conventional MTPA control inevitably generates torque ripple because of the spatial harmonics of IPMSM. This paper proposes a voltage feedforwarding control to suppress the torque ripple. As the rotating speed increases, the feedforwarding voltage gets larger. Over a certain speed, the feedforwarding voltage is large enough to be over the inverter voltage limitation. And the torque ripple reduction performance is significantly degraded. Even, the average torque cannot match the torque command, since the fundamental frequency voltage is also affected by the voltage saturation. This study proposes a novel technique that can apply the voltage feedforwarding control up to medium speed range. By preventing the saturation of the inverter's output voltage, it is possible to reduce the torque ripple effectively in the speed range where the conventional method cannot reduce the torque ripple. The proposed method is verified through simulations and experimental results with 45 kW IPMSM for Hybrid Electric Vehicle (HEV) drive system.