Grid synchronization of doubly-fed induction generator using integral variable structure control

This paper proposes a novel direct voltage control scheme, using integral variable structure control to synchronize a doubly fed induction generator (DFIG)-based wind energy conversion system (WECS) to the grid. The proposed scheme directly controls the stator terminal voltage of the DFIG to track the grid voltage without current control loop; hence, the structure of controller is simplified. The control scheme includes parametric uncertainty and external disturbances into the formed design procedure; hence, the proposed scheme has better robustness than existing synchronization methods. Both computer simulation and hardware implementation results are presented to demonstrate the advantages of the proposed scheme.