IMPROVEMENT IN DIRECT TORQUE CONTROL OF INDUCTION MOTOR USING FUZZY LOGIC DUTY RATIO CONTROLLER

Abstract

This paper shows the application of fuzzy logic based duty ratio control technique to reduce torque ripple in an induction motor employing Direct Torque Control (DTC). This technique increases the number of voltage vectors beyond the available eight discrete voltage vectors without any increase in the number of semiconductor switches in the inverter. Look-up Table based on-line tuning PI controller is proposed for outer speed control loop to achieve swift response, less overshoot and precision speed control to have wide torque-speed characteristics. A new algorithm for optimized value of stator flux based on the maximum reference value of electromagnetic torque is proposed to operate in conjunction with duty ratio control. The performance of the proposed drive system is evaluated through digital simulation using MATLAB-SIMULINK package. The simulation results clearly depict the superiority of devised method over the existing methods of DTC.