Improved Direct Torque Control of Induction Motor Drives to Reduce Torque Ripple

Abstract

The Direct Torque Control (DTC) is an advanced scalar control technique, which is used to obtain high performance torque control. This dissertation work is aimed to give a detailed comparison between two scheme of the DTC i.e. conventional DTC and SVM-DTC. The study is done by simulation using MATLAB/Simulink power system block set that allows a complete representation of the power section (inverter and induction motor) and the control system.

In this thesis, the performance of the two DTC scheme is evaluated in terms of torque and current ripple, and transient response to step variations of the torque command, and emphasizing advantages and disadvantages. In conventional DTC, the torque and current ripple both are high. This undesired torque and current ripple is reduced by using the space vector modulation (SVM) depends on the reference torque and flux i.e. SVM-DTC. SVM-DTC technique has several advantages that offering lower torque ripple, better DC bus utilization, lower switching loss, lower total harmonic distortion in motor current and easier to implement in digital system. The analysis has been carried out on basis of the result obtained by simulations.