Sensorless direct torque and flux control of an IPM synchronous motor drive at low speed and standstill

This paper investigates a sensorless direct torque and flux control (DTFC) scheme for IPM synchronous motor (IPMSM) drives at low speed and standstill. Closed-loop control of both the torque and stator flux linkage are achieved using two proportional-integral (PI) controllers. A high frequency signal injection technique is utilized at low speeds to obtain the rotor position information. The hybrid current-voltage model flux observer with a smooth handover algorithm estimates the stator flux linkage over the whole speed range. The sensorless method is capable of zero-speed full load operation. Experimental results confirm the effectiveness of the proposed sensorless SVM-DTFC system.