Direct torque control of induction motors based on fuzzy DSVM strategy

To solve the problems of large torque ripples, current distortion, flux depression and unstable switching frequency in low speed range in conventional direct torque control system of induction motor, a modified strategy was proposed based on the technology of discrete space vector modulation (DSVM) and fuzzy control. Controlling period was divided into m time slices, in which a voltage vector outputs forming space voltage vector. And then switching stable was optimized by new space voltage vector. The fuzzy logic controller was used to select the voltage vector instead of the conventional hysteresis controllers. Simulation results prove that the application of the improved DSVM-DTC and the fuzzy DSVM-DTC strategy improves the low speed performance of direct torque control effectively. While maintaining the switching frequency constant, flux depression and current harmonious decomposition are overcome remarkably, and the average of torque ripple reduces to 3.1%.