Patent ID: 8076790

Claim:
A wind turbine generator system including switching means arranged at a stator side of a doubly fed generator for linkage with a grid and a converter for exciting a secondary winding of the doubly fed generator, a rotor of the doubly fed generator coupled to a wind turbine for generating electric power, comprising: first detection means for detecting a stator voltage at the switching means on the stator side of the doubly fed generator; second detection means for detecting a grid voltage at the switching means on the side of the grid; third detection means for detecting a rotation phase of the doubly fed generator; means for obtaining a slip frequency from the voltage of the grid and the rotation phase for the converter to effect excitation from a secondary side of the generator; first controlling means for decreasing a difference in amplitude between the grid voltage and the stator voltage when the switch is open to equalize the stator voltage generated by excitation on the secondary side with the grid voltage; and second controlling means for decreasing a difference in phase between the grid voltage and the stator side voltage by further controlling the slip frequency to control the converter when the switch is open to synchronize the stator voltage generated by excitation on the secondary side with the grid voltage.