Abstract: Methods of measuring a stall condition of a rotor of a wind turbine are disclosed. In one aspect a stall parameter is obtained on the basis of the power parameter and a thrust parameter; and the stall parameter compared with a threshold to determine a stall condition of the rotor.

Abstract: A method of controlling a wind turbine blade of a wind turbine comprising: providing data comprising a plurality of pitch angles of the wind turbine blade and corresponding expected power coefficients for the wind turbine, each pitch angle corresponding to a maximum expected power coefficient for a degradation state of the wind turbine blade; obtaining a current power coefficient of the wind turbine; determining a desired pitch angle for the wind turbine blade, the desired pitch angle being equal to a pitch angle from the dataset corresponding to an expected power coefficient equal to the current power coefficient; and changing a pitch angle of the wind turbine blade to the desired pitch angle.

Abstract: Methods of measuring a stall condition of a rotor of a wind turbine are disclosed. In one aspect a stall parameter is obtained on the basis of the power parameter and a thrust parameter; and the stall parameter compared with a threshold to determine a stall condition of the rotor.

Abstract: The present invention relates to a method of controlling a wind turbine comprising a tower supporting a rotor comprising a plurality of pitch-adjustable rotor blades. The method includes obtaining a movement signal indicative of a lateral movement of the tower; determining a pitch modulation signal, based on the movement signal, for actuating a rotor blade to produce a desired horizontal force component to counteract the lateral movement of the tower; determining a radial force component acting on a rotor blade; determining a phase offset parameter for the rotor blade based on the radial force component; and, transforming the pitch modulation signal into a pitch reference offset signal for the rotor blade based on the phase offset parameter.

Abstract: A method of controlling a wind turbine is provided, comprising identifying an out-of-vertical load acting in a first direction on the wind turbine. A direction of a wind load acting on the wind turbine is determined. If there is a degree of alignment between the direction of the wind load and the first direction, the wind turbine is controlled to reduce the wind load.

Abstract: There is provided a method of controlling power output of a wind turbine at below-rated wind speed, the method comprising: determining an indication of blade torsion of one or more rotor blades of the wind turbine in dependence on wind speed and/or rotor speed; determining a torsion-corrected blade pitch based on the indication of blade torsion; and using the torsion-corrected blade pitch to control pitch the one or more rotor blades.

Abstract: The present invention relates to a method of controlling a wind turbine comprising a tower supporting a rotor comprising a plurality of pitch-adjustable rotor blades. The method includes obtaining a movement signal indicative of a lateral movement of the tower; determining a pitch modulation signal, based on the movement signal, for actuating a rotor blade to produce a desired horizontal force component to counteract the lateral movement of the tower; determining a radial force component acting on a rotor blade; determining a phase offset parameter for the rotor blade based on the radial force component; and, transforming the pitch modulation signal into a pitch reference offset signal for the rotor blade based on the phase offset parameter.