| Summary: | Doubly fed induction generator (DFIG) based wind turbines have been found to be very sensitive to asymmetrical grid fault, wherein the harmful oscillations in the electromagnetic torque has being made a big concern. What makes things harder is that latest grid codes require grid-connected wind turbines to possess the ability of positive- and negative-sequence reactive current supporting. Hence, it becomes a guide mechanism to meet the grid codes and to ensure the operation safety of the wind turbines. Even though a tradeoff could be made between them, it is still quite difficult to coordinate the current dispatch of the DFIG's rotor- and grid-side converters (RSC and GSC), since there are totally eight currents needing to be carefully designed, i.e., the positive- and negative-sequence active and reactive currents in each converter. To address this issue, this article analyzes the reactive current constraints in detail, based on which a coordinated reactive current control strategy is put forward for the DFIG-based wind turbines during asymmetrical grid condition. Simulation studies demonstrate the effectiveness of the proposed strategy.
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