Design and implementation of a predictive controller for reducing the torque ripple in direct torque control based high frequency 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 in the beginning of each sampling period and its expected value in the end of period is predicted according to an extrapolation algorithm. This algorithm is performed by calculating the slope of stator current variation according to the stator flux variation. Thus, there is no need to solve the high order equations of machine. The calculation of 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 frequency drives where the sampling frequency is high and there is no adequate time for extra complex calculations. Simulation and experimental results confirm the ability of this method to reduce the torque ripple.