Fuzzy Direct Torque Control of Surface Permanent Magnet Synchronous Motor

To solve the problems of large torque and flux ripple in direct torque control (DTC) of permanent magnet synchronous motors (PMSM), a fuzzy controller is used to replace hysteresis comparators and switching tables in the DTC. Different from the conventional fuzzy controller which only outputs the angle or amplitude of the voltage vector, the controller adjusts the angle and value of the voltage vector at the same time in the surface PMSM DTC system is proposed. The inputs and output of the fuzzy controller are: stator flux, torque error, angle and amplitude of voltage vector in stator flux coordinate system. The simulation results of proposed fuzzy control system work normally. Compared with conventional fuzzy control systems, stator flux and torque ripples are decreased and only when motor speed is negative, torque ripple is a little higher. To suppress torque ripple at negative speed, two membership functions of torque error are designed and the fuzzy control system can select the proper membership function according to motor speed. Simulation results show adaptive fuzzy control system can effectively reduce torque and flux ripple in four quadrants.