An investigation of direct and indirect torque controllers for PM synchronous motor drives

This paper presents a comparative study of two popular torque control schemes which have evolved for PM synchronous motor drives in recent years. The current regulated torque control strategy which has been well established for a number of years and which exercises control in the rotor reference frame is compared with the direct torque control (DTC) scheme where current controllers followed by PWM or hysteresis comparators and dq transformations are not used. Accuracy of torque control in the face of variation of parameters of importance are discussed followed by the problems of implementation of either approaches. Experimental results comparing both strategies of torque control are presented.