Study of Induction Motor Drive With Direct Torque Control SCHEM Using Space Vector Modulation and Fuzzy Logic Controllers

Abstract

Among all control methods for induction motor drives (IMD), Direct Torque Control (DTC) is the one which is independent of machine rotor parameters. DTC is simple and allows torque control in both steady and transient state. In DTC the torque and flux can be controlled with help of hysteresis control in which it suffers from high torque and flux ripples due to variable switching frequency. The Space Vector Modulation (SVM) is used to reduce the torque and flux ripples of IM and maintain constant switching frequency. Hence, it is very easy to design the filter for reducing torque and flux ripples.
In this thesis fuzzy controllers are also used along with the SVM. The proposed fuzzy based DTC-SVM results in reducing the torque ripple. The Fuzzy-PI Controller (FPIC) to achieve precision speed control and Fuzzy Logic Duty Ratio Control (FLDRC) is used to minimize torque & flux ripple. When Fuzzy Logic is used for the on-line tuning of the PI controller, it receives scaled values of the speed error and change of speed error. Its output is updating in the PI controller gains based on a set of rules to maintain excellent control performance even in the presence of parameter variation and drive non-linearity of the system.