Patent ID: 7692323

Claim:
A wind turbine generator system including a doubly fed generator having a stator and a rotor, a switch arranged on a side of the stator for linkage with a grid, and a converter for exciting a secondary winding of the doubly fed generator, the rotor being coupled to a wind turbine for generating electric power, comprising: 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; calculating means for calculating a slip frequency from a phase of the grid voltage and the rotation phase; phase controlling means for controlling the converter to excite the secondary winding on the basis of the slip frequency so as to decrease a difference between a phase of the stator voltage and a phase of the grid voltage, when the switch is open; and controlling means for closing the switch when the phase of the stator voltage is identical with the phase of the grid voltage, wherein the controlling means closes the switch when the stator voltage is identical with the grid voltage in amplitude and comprises means for using a compensation phase value calculated by the second controlling means for further synchronizing operation.