Ride-through strategy for DFIG wind turbine systems using dynamic voltage restorers

This paper investigates the application of a dynamic voltage restorer (DVR) to assist with the uninterrupted operation of a wind turbine driving a doubly-fed induction generator (DFIG), connected to a power network, during grid faults. In order to reduce the power rating of the DVR, the control schemes of rotor-side converter and pitch angle of the DFIG and DVR are suitably designed and coordinated. For DVR control, digital all-pass filters are used for extracting the positive-sequence component of the grid voltage. Using the positive-sequence component, the phase angles of the positive-and negative-sequence components of the grid voltage are derived. Thus, dual voltage controllers are implemented for these two sequence components in the dq synchronous reference frame. PSCAD/EMTDC simulations show the effectiveness of the proposed technique and a feasibility of reducing the cost of DVR for the fault ride-through (FRT) capability of DFIG. The validity of the proposed control scheme for the DVR has also been verified by experimental results.