A new direct torque control scheme for PMSM with on-line stator resistance tuning

The electromagnetic torque in a PMSM is proportional to the angle between the stator and rotor flux linkage, thus, high dynamic response can be achieved by means of direct torque control. The main advantage of DTC is its simple structure since no coordinate transformations or PWM generation are needed. In this paper, an improved scheme to solve the torque and the stator flux linkage ripples of direct torque control (DTC) for a permanent magnet synchronous motor is proposed. Moreover, the fuzzy DTC control strategy based on fuzzy controller using the space vector modulation (SVM) is designed and presented in this paper. The variation of stator resistance due to changes in temperature or frequency degrades the performance of DTC controlled by introducing errors in the estimated flux linkage vector and the electromagnetic torque. Compensation for the effect of stator resistance variation then becomes necessary. Estimation of the stator resistance and its compensation using a PI estimation has been proposed in this paper.