Analysis and Simulation of Direct Torque Controlled Induction Motor Drive

Abstract

The vector control study of an induction motor countenances the decoupled analysis. In this control torque and flux components are independently controlled (just as in dc motor). This simplifies the analysis compared to the per phase equivalent circuit. The major disadvantage of flux vector control is the required insertion of the pulse encoder. The other disadvantage is that torque is indirectly controlled rather than directly. Lastly, a delay in signal of input references and resultant stator voltage vector is introduced because of presence of the PWM modulator. The last two factors prevent the eventual capability of vector control to attain high express flux and torque control. Direct torque control (DTC) of an induction motor fed by a voltage source inverter is a modest scheme that does not need lengthy computation time and can be implemented without pulse encoders and is unresponsive to parameter variations. The objective is to control efficiently torque and flux. This procedure estimates motor flux and torque by sampling and analyzing motor terminal voltages and currents. A voltage vector is nominated to have flux and torque errors within boundaries, built on estimations of flux position and amount of instantaneous errors in torque and stator flux. This method made the motor control more accurate and fast, highly dynamic speed response and simple to control. The reference value can be evaluated using the flux and torque estimated and motor parameters. The effectiveness of the Direct Torque Control scheme was verified by simulation using MATLAB/SIMULINK®.