Controlling the doubly fed induction generator based wind turbines during normal and disturbed grid voltage

Abstract

This work presents an improved strategy in the field of predictive control (PC) of the doubly fed induction generator (DFIG). The proposed strategy applies four voltage vector in every period in order to have constant switching frequency and low current THD. The appropriate voltage vectors in each period are recognized when the estimated duration times of selected active vectors are positive. The suggested techniques has excellent performance during transient and steady – state conditions. The proposed predictive control can easily flow the references under normal and abnormal voltage conditions even if the references contain ac terms. Without any additional controller, the proposed technique could obtain smooth stator active and reactive power or smooth electromagnetic torque or could inject sinusoidal and balance current into the grid when the voltage unbalance appears in the stator winding of DFIG. Moreover, under unbalanced voltage conditions, still four voltage vectors are applied in every switching period. The simulation studies for this technique are carried out for 2 MW DFIG in Matlab Simulink environment under ideal and unbalanced grid voltage. Furthermore, the experimental studies are now conducting. The results of this technique are compared to other strategies. The comparisons show that the performance of the proposed strategy is significantly superior to the other strategies.