Patent ID: 8269361

Claim:
Method of determining quality of an initial value for a blade pitch angle of a wind turbine, comprising: measuring an initial power captured by the wind turbine, while the blade pitch angle has the initial value; changing the blade pitch angle from the initial value to a first value by a predetermined first angle change in a first direction; measuring a first power captured by the wind turbine, while the blade pitch angle has the first value; changing the blade pitch angle from the first value to a second value by a predetermined second angle change in a second direction being opposite to the first direction; measuring a second power captured by the wind turbine, while the blade pitch angle has the second value; calculating a power difference between the first power and the second power; and determining the quality of the initial value based on the calculated power difference, wherein measuring the initial power comprises an averaging process within an initial time interval, measuring the first power comprises an averaging process within a first time interval, and measuring the second power comprises an averaging process within a second time interval, and wherein the first time interval starts after an elapse of a predetermined first waiting time following an approach of first value, and the second time interval starts after an elapse of a predetermined second waiting time following an approach of second value.