This paper reports results of further investigation of the direct torque control to a permanent magnet synchronous motor drive. A variable parameters speed controller is proposed from the point of view of speed control to accelerate the dynamic response and increase the control precision and decrease the torque ripple of the system. It is presented that a reference flux vector calculation direct torque control system with a speed controller using different proportional and integral coefficients, and a novel torque-limiting method is recommended. The simulation results show that the control system can improve its performances and limit torque ripple effectively.
