Direct-driven permanent magnet synchronous generator (PMSG) has become an important research subject besides the double-fed induction generator. With the increasing of unit capacity, the study of topology of high power converters based on multi-level converter is attracting more and more attention. The study of vector control of the direct-driven permanent magnet synchronous wind turbines based on three-level converter is carried out in this paper. Based on the maximum wind-energy capture control of the PMSG, the unity power factor operation of PMSG is realized by controlling the d-axis current to zero in the generator-side converter. A detailed comparative study of two-level system and three-level system is conducted. The simulation results verify the validity of this algorithm.