Sensorless Direct Torque and Flux Controlled Interior Permanent Magnet Synchronous Motor Drive Incorporating Field Weakening

Abstract

This paper presents a sensorless space vector modulation (SVM) direct torque and flux control (DTFC) scheme for interior permanent magnet (IPM) synchronous motors. Closed-loop control of both the torque and stator flux linkage is achieved via two proportional-integral (PI) controllers. The reference voltage vectors are generated by a SVM unit, which replaces the switching table in the conventional direct torque control (DTC) scheme. For sensorless operation, a speed observer based on the stator flux linkage is investigated in this paper. The speed estimator is simple, software-based and irrespective to machine parameters. Hence, the basic advantages of a DTC controller are retained. The operating range of the DTFC drive is extended into the high speed region by incorporating flux weakening. Experimental results confirm the effectiveness of the sensorless DTFC scheme.