Patent ID: 8043055

Claim:
A wind turbine generator system comprising: a nacelle for supporting a wind turbine rotor; a rotation mechanism for performing a yaw rotation of the nacelle; a wind direction measurement apparatus for measuring a present wind direction; and a control apparatus for controlling said rotation mechanism, wherein said control apparatus is configured to calculate a wind direction deviation from the present wind direction measured by said wind direction measurement apparatus and a direction of said wind turbine rotor, wherein said control apparatus is configured to perform a yaw rotation of said nacelle by said rotation mechanism when a first condition is satisfied, said first condition being a condition under which a state where an absolute value of said wind direction deviation exceeds a first threshold value and continues for a predetermined first duration, and wherein said control apparatus is configured to perform a yaw rotation of said nacelle when a second condition is satisfied, said second condition being a condition under which a state where the absolute value of said wind direction deviation exceeds a second threshold value smaller than said first threshold value and continues for a second duration longer than said first duration.