Design and implementation of a predictive controller for reducing the torque ripple in direct torque control based induction motor drives

In Direct Torque Control, selection of each voltage vector is based on the measured parameters in the beginning of the sampling period. Due to the fast dynamic of torque, this delay causes an extra torque ripple. In this paper, a new predictive controller is proposed for compensating this delay and reducing the torque ripple. The stator current is measured two times at the beginning of each sampling period and its expected value at the end of period is predicted according to an extrapolation algorithm. Thus, there is no need to machine parameters and the algorithm is quite robust against machine parameters variations. The calculation of the electromagnetic torque is performed using the predicted value of stator current. Therefore, the selection of voltage vector is more realistic and it prevents extra torque ripple. This controller is very suitable for high power drives where the sampling frequency is low and there is adequate time for the extra measurements. Simulation and experimental results confirm the ability of this method to reduce the torque ripple.