Study in direct torque control of induction motor by using space vector modulation

Abstract

In conventional direct torque control (DTC) has, over the years, become of the most popular methods of control for induction motors (IM) drive system. A single stator voltage vector of the inverter standard topology is selected every control sampling period, and it is maintained for the whole period. This makes the torque and stator flux reference values to be reached quickly, with a small number of inverter switching, resulting in a very good dynamic response. However, by this switching technique, based on hysteresis, large and small torque and flux errors are not distinguished, which cause an extra torque ripple in motor steady state operation.. A control is proposed to determine the reference value of the flux according to the value of the motor torque. The results of the Matlab- Simulink simulations with different algorithms such as classical DTC, SVM-DTC method and SVM-DTC with PI controller direct torque control without hysteresis band has been compared.. The average torque ripple is reduced over 60% with SVM-DTC with PI controller method compared with classical DTC and is reduced by 30% compared with SVM-DTC.