Abstract: The modeling of direct torque control system of permanent-magnet synchronous motor based on MATLAB/Simulink was introduced, and the simulation of the system was carried out to research on the effect of PI controller parameters on the system performances.Also , the relationship between torque hysteresis loop' s width and torque ripple amplitude was analyzed.The results show that the direct torque control system gives a good response to the rotation speed and torque , and that the torque ripple amplitude decreases with the reduction of torque hysteresis loop' swidth.The PI controller parameters K p and K i should be properly matched to achieve
excellent system performance , for a large scaling factor K p will accelerate the system' s dynamic response, while the integral coefficient K i mainly influences the system' s static error.

Key words: synchronous motor, direct torque control, simulation, MATLAB/Simulink modeling