Simulation of improved direct torque control system for permanent magnet synchronous motor

The main disadvantage is of high torque ripple at low rate. An important reason is that stator resistance value changes for the phenomenon of rising temperature and changing current frequency when motor is running. Thus the estimation precision of stator flux decreases, leading to high electromagnetic torque ripple. Aiming at this problem, a direct torque control system of permanent magnet synchronous motor is devised. According to the error between actual torque and reference torque, a means for compensating stator resistance variation using PI controller is proposed. The simulation results show that the control system can reduce the flux and torque ripple. The running performance of system is improved and the robustness to parameters variation is enhanced.