Reducing Variation of Switching Frequency in Finite-State Predictive Torque of three-Phase Induction Motor

In this research, a new technique is applied to the predictive direct torque control of the induction motor in order to reduce the variation of the switching frequency. The method is a modification of the finite set model predictive control (FS-MPC). In this method, the switching options are examined in a cost function and the best option is selected based on the minimum cost function. Since the switching technique in FS-MPC is direct switching without using a modulator, the switching frequency will be variable. In the proposed method, the periodic selection of the active and zero voltage vector is used to reduce the variation of the switching period. Thus, the zero voltage is mandatorily exerted after an active voltage and vice versa. With this method, the cost function is only examined for the active voltage vectors and the zero voltage is selected for the next control interval. This manner is repeated in the whole algorithm. The proposed method is evaluated by simulation via MATLAB/Simulink. The results showed that the proposed method reduced the variation of the switching frequency and it was stable for the different operating point.