Speed ripple reduction for an interior permanent-magnet synchronous motor based on sensorless voltage-current phase difference control

This paper proposes speed ripple reduction for an interior permanent-magnet synchronous motor (IPMSM) controlling phase difference between the armature voltage and current. The IPMSMs are controlled with a rotor position sensor or by a sensorless control method. Voltage-current phase difference control is one of the sensorless drives with low cost and simple structure. However, if the load varies depending on the rotor position the speed ripple occurs by torque fluctuation. This is because the voltage-current phase difference control is based on the V/f control and it uses neither position sensor nor speed estimation. In this paper, the amplitude of armature voltage is changed according to the load torque variation. Both simulation and experimental results show effectiveness of the proposed system.