Torque control for IPMSM in the high speed range based on voltage angle

In a motor control, a voltage saturation is a serious problem as a motor speed increases. To solve the problem, various field weakening methods were studied for a long time. The field weakening methods with PI current controllers are normally used, however the voltage angle control without PI current controllers is receiving attention because of its simple implementation. In this work, the field weakening method is proposed based on the voltage angle control. A inner d-axis current loop is added for stability and the root locus is utilized to verify stability according to loop gains and loop structures. Moreover, a six-step operation is applied to expand the voltage utilization in this paper. Various simulations and experiments were conducted to verify the proposed method.