LVRT capability and improved control scheme of PMSG-based WECS during asymmetrical grid faults

Low voltage ride-through (LVRT) requirements for wind energy conversion systems (WECSs) under asymmetrical grid faults are still under discussion. In a draft code “SDLWindV” of Germany, wind energy conversion systems (WECSs) are demanded to inject positive-sequence reactive current during asymmetrical faults, which represents the future trends of LVRT requirements for asymmetrical faults. However, such new requirements are not taken into account in most of the existing LVRT control schemes. In this paper, the capability of permanent magnet synchronous generator (PMSG)-based WECSs to fulfill such new requirements is evaluated, considering the voltage and current limitations of grid-side converter (GSC).Further, based on the analysis of the LVRT capability, a control scheme is proposed for PMSG-based WECSs to satisfy the new requirements. Finally, both simulations and experimental tests are carried out to verify the proposed scheme. The achieved analysis results of asymmetrical faults ride-through capability of PMSG-based WECS will provide a guideline for the design of grid codes, and the proposed scheme is expected to help PMSG-based WECSs meet the new LVRT requirements for asymmetrical faults.