An improved direct torque control of induction machines

The direct torque control (DTC) of induction machines with conventional hysteresis comparators suffer from variable switching frequency. This is simply because of the variable torque slope which depends on the operating conditions. An innovative, simple and new torque controller which can offer a constant torque switching frequency is proposed. To improve the performance of the DTC drive further, a simple stator flux compensator is also proposed. The compensator corrects the steady state stator flux phase and magnitude errors and thus improve on the torque estimation and drive performance. Simulation and experimental results are presented to validate the proposed schemes.