Abstract: A viable alternative to adjust speed over a wide range at minimal cost using a doubly fed induction generator for wind turbines was introduced. The vector control system by DFIG mathematic models was analyzed. Three kinds four-quadrant power converters were discussed. During a low speed, the pitch angle is a constant, wind turbines keep on the optimum speed ratio between the pitch and wind so as to absorb the maximum energy. During a high speed, wind turbines absorb or release partial energy, and the mechanical stress were less.