A new control strategy of WFSG-based wind turbine to enhance the LVRT capability

• A novel control strategy of WECS based on WFSG and interconnected to the grid.
• The paper improves the LVRT capability of WFSG under unbalanced voltage dips.
• Use of DC chopper circuit to protect the inverter and DC-link capacitor.
• A frequency locked loop algorithm in order to extract the positive sequence and control it.
• The performance has been demonstrated under varying wind and grid fault conditions.

This paper proposes a competent and effective scheme to enhance the low voltage ride through (LVRT) capability of wound field synchronous generator (WFSG) based wind turbines (WTs) under unbalanced voltage dip conditions. A technique for grid synchronization against voltage excursions, i.e., a PLL using positive grid voltages with a high selectivity filters (HSFs) is utilized to extract a robust grid voltage synchronization signal irrespective of the mains condition to enhance the overall system performance. Besides, a new controller (adaptive fuzzy RST) for both the stator side converter (SSC) and grid side converter (GSC) current regulation are employed to further improve dynamic performance. Also, a reactive power support scheme to manage the WFSG reactive power during contingencies and fulfill the grid codes obligations is presented. Moreover, an additional device such as braking chopper (BC) circuit is used in the DC-link circuit for stable operation of the wind energy conversion system (WECS) under-line fault. Effectiveness of the proposed control strategy is verified by the numerical simulations.