Predictive direct torque and flux control of doubly fed induction generator with switching frequency reduction for wind energy applications

Abstract

A model based predictive torque and flux control (PTFC) is proposed in this paper for doubly fed induction generator (DFIG) applied in wind energy applications. Different from the conventional switching-table-based direct torque control (DTC), which selects the output vector from a switching table, the developed PTFC selects the most suitable vector minimizing the errors of rotor flux and torque based on predictions of their evolutions versus time. Compared to DTC with the same sampling frequency, there are significant reductions in both torque and flux ripples for PTFC with lower switching frequency, while their dynamic performances are similar. Furthermore, by incorporating the frequency reduction in PTFC, the average switching frequency can be reduced up to 38.76% without affecting its performance. The results of PTFC operating at a very low switching frequency of below 550 Hz are presented, validating the capability of PTFC to satisfy the low switching frequency requirement of high power wind energy applications. Simulation results are presented to validate the effectiveness of the proposed PTFC.