Method to individually optimize respective pitch angles of a plurality of blades in a wind turbine

A method to individually optimize respective pitch angles of a plurality of blades in a wind turbine, the method comprising:

• a) supplying a modulation signal having a predefined modulating frequency to modulate at the modulating frequency a pitch angle of only a respective one of the plurality of blades being presently optimized;
• b) filtering output power of the wind turbine subject to the modulating frequency to extract a power signal in a frequency spectrum comprising at least the modulating frequency;
• c) mixing the extracted power signal and a demodulation signal oscillating at the modulating frequency to generate a signal comprising a product of the extracted power signal and the demodulation signal;
• d) filtering the generated signal to remove at least the modulating frequency and extract a gradient signal effective to search a pitch angle estimate conducive to optimize output power of the turbine;
• and
• e) integrating the gradient signal to cause the gradient signal to converge towards a value indicative of an optimal pitch angle for the respective one of the plurality of blades being presently optimized.