Patent ID: 8476780

Claim:
A wind turbine generator in which an orientation of a nacelle is variably controlled so as to follow a wind direction, the wind turbine generator comprising: a wind direction detecting means that detects a main wind direction; a wind direction assuming means that assumes an actual wind direction, which is a direction of wind which blows in actual use, by assuming a wind direction offset value, which is a deviation between the main wind direction and the actual wind direction, at a predetermined wind speed; an average-generator-output-power calculation means that calculates an average generator output power for a predetermined period of time in the actual wind direction which has been assumed; and an actual wind direction estimation means that estimates the actual wind direction by approximating the average generator output power with respect to the wind direction offset value which has been assumed to a quadratic curve and estimating the wind direction offset value at the time when the average generator output power is the maximum in the quadratic curve which has been approximated to be an actual offset value.