Direct Torque and Flux Regulation of an IPM Synchronous Motor Drive Using Variable Structure Control Approach

To enhance high performance of an interior permanent magnet synchronous motor drive, a nonlinear variable structure controller is proposed for the control of torque and stator flux linkage. The modeling and experimental results show that the torque and flux ripples have been significantly minimized. The fast responses and robustness merits of the classic direct torque control are preserved by eliminating hysteresis and the existing proportional-integral controllers of torque and flux. By replacing the open-loop flux and torque estimator with a closed-loop observer, the drive system has achieved high performance at very low speed, down to 10 rpm (0.33 Hz) with half full load.