Wide speed operation of a direct torque and flux controlled IPM synchronous motor drive without a mechanical sensor

This paper investigates a sensorless direct torque and flux control (DTFC) scheme based on space vector modulation (SVM) for interior permanent magnet synchronous motor (IPMSM) drives over a wide speed range. Closed-loop control of both the torque and stator flux linkage are achieved by using two proportional-integral (PI) controllers. The reference voltage vectors are generated by a SVM unit. A high frequency signal injection technique is adopted 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 operating range of the sensorless DTFC drive is extended into the high speed region by incorporating field weakening. Experimental results confirm the effectiveness of the proposed method.