A novel LVRT strategy for direct-drive wind turbines based on permanent magnet synchronous generator

Increasing penetration level of wind energy into the power system over the last decades has brought new issues and challenges. One of these concerns is the issue of low voltage ride through (LVRT). In this paper, given the characteristics of MW-level direct-drive wind turbines based on permanent magnet synchronous generator, a novel LVRT strategy is proposed, which is the combination of coordinate control of generator-side and grid-side converters and small un-loading branch. The implementation principle as well as calculation criteria are explained in depth. Finally, the feasibility of the proposed method is demonstrated by simulation results under balanced and unbalanced sag conditions.