Direct Torque Control Strategies of Induction Machine: Comparative Studies

The direct torque control (DTC) was proposed as an alternative to the vector control in the middle of 1980s for AC machine control. This strategy bases on the direct determination of inverter switching states and offers a simpler scheme and less sensitivity to machine parameters. However, the variable switching frequency of DTC causes high flux and torque ripples which lead to an acoustical noise and degrade the performance of the control technique, especially at low-speed regions. In the objective of improving the performance of DTC for the induction motor, this work addresses the most important points concerning this issue. The reduction of high ripples, which are the major drawbacks, by applying a constant switching frequency using the space vector modulation (SVM) has been done firstly. Then, fuzzy DTC-SVM strategy with adaptive fuzzy-PI speed controller has been proposed. The results of all the discussed aspects of this chapter have been obtained by numerical simulation using MATLAB/Simulink software.