Direct torque control (DTC) of induction machines is known to have a simple control structure with comparable performance to that of the field-oriented control technique. Two major problems that are usually associated with DTC drives are: 1) switching frequency that varies with operating conditions and 2) high torque and flux ripples. To solve these problems, and at the same time retain the simple control structure of DTC, a constant switching frequency torque controller is proposed to replace the conventional hysteresis-based controller. In this paper, the modeling of proposed controller followed by simulation and experimental results are presented. The proposed controller is shown to be capable of reducing the torque and flux ripples and maintaining a constant switching frequency |
