An improved direct torque control of induction motor with current hysteresis band

In industrial application, many topics have been investigated to improve the control performances of AC drive systems. Direct torque control (DTC) of induction machine is one of the control schemes. In this paper, the cause of the great impulse start-up current of induction machine employing direct torque control is analyzed, in order to ensure the motor start with maximum torque, and also ensure the system operate properly, it is very important to control the stator current. Then an improved control scheme with current hysteresis band control for DTC is proposed. It makes use of the characteristic of direct torque control having zero state vectors. It is not only effective to limit the impact start-up current, but also is effective in steady state operation. To evaluate the performances of the proposed scheme, simulation studies were performed. The results illustrate that the proposed scheme with current hysteresis band control has satisfactory performances.