Recently　offshore　wind　power　have　developed　rapidly.　As　the　mainstream　generator　of　offshore　wind　farm,　permanent　magnet　synchronous　generator　(PMSG)　has　been　increasingly　applied　in　offshore　wind　farm.　The　operating　performance　of　PMSG　based　wind　energy　conversion　system　(WECS)　depends　on　the　performance　of　control　system,　which　relies　on　the　accurate　measurement　of　phase-locked　loop　(PLL).　This　paper　propose　a　modified　PLL　scheme　to　improve　system　stability.　A　DC-link　voltage　relaxation　control　strategy　is　also　applied　to　obtain　a　fast　response　and　lower　over-voltage　level,　which　can　lead　to　better　control　performance　and　reduced　cost.　Small　signal　stability　analysis　as　well　as　simulation　results　verified　that　the　optimized　system　have　greater　stability　and　better　performance.　©　2019　IEEE.