Techniques for Improvements of the Performances of Direct Torque Control Strategy for Induction Motor

The basic concept of direct torque control of induction machines is investigated in order to emphasize the effects produced by a given voltage vector on stator flux and torque variations. The low number of voltage vectors which can be applied to the machine using the basic DTC scheme may cause undesired torque and current ripple. An improvement DTC schemes proposed in the research literature is presented and compared with the classical. In this paper, we propose two approach’s of improvement of Direct Torque Control (DTC) of Induction motor, first is Discrete Space Vector Modulation (DSVM_DTC) Where the Stator flux and torque are controlled using respectively by five-level hysteresis comparators, second is and The discrete time direct torque control (DTDTC) requires voltage and current measurements to calculate the back-EMF, and address the problem with torque ripple in the basic DTC system is introduced. Numerical simulations tests have been carried out to validate the proposed method.