Low-Speed and Standstill Operation of a Sensorless Direct Torque and Flux Controlled IPM Synchronous Motor Drive

This paper investigates a sensorless direct torque and flux control scheme for interior permanent magnet synchronous motor drives at low speeds, including standstill. Closed-loop control of both torque and stator flux linkage are achieved by using two proportional-integral controllers. The reference voltage vectors are generated by a space vector modulation unit. A high-frequency signal injection technique is adopted at low speeds to obtain the rotor position information. A hybrid current-voltage model flux observer with a smooth handover algorithm estimates the stator flux linkage over the whole speed range. Experimental results confirm the effectiveness of the proposed method.