Patent ID: 7847427

Claim:
A wind turbine generator system including a doubly fed generator including a stator and a rotor, comprising: a switch arranged on a side of the stator for linkage with a grid; a converter for exciting a secondary winding of the doubly fed generator, the rotor being coupled to a wind turbine for generating electric power; a controller configured to control the converter; first detecting means for detecting a stator voltage at the switch on a side of the stator; second detecting means for detecting a grid voltage at the switch on a side of the grid; third detecting means for detecting a rotation phase of the doubly fed generator; wherein the controller controls excitation of the secondary winding to control an amplitude and a phase of the stator voltage; and controlling means for closing the switch when the phase of the stator voltage is identical with the phase of the grid voltage and the stator voltage is identical with the grid voltage in amplitude, wherein the controller generates a torque current command after the controlling means closes the switch).