Abstract: The present invention relates to control of a wind turbine to reduce structural loading due to vibrations of the blades along the edgewise direction. A rotor control system for actuating pitch of pitch-adjustable rotor blades of a wind turbine is disclosed. Pitch modification signals are determined based on edgewise load signals for each of the rotor blades. The edgewise load signal are coordinated transformed and input into a primary whirling controller unit to provide whirling signal components which can be used for determining the pitch modification signals.

Abstract: A method of designing a wind turbine rotor blade. The method includes selecting a gravity load safety factor associated with wind turbine rotor blade fatigue loading due to gravity, that is selected to be less than a defined wind load safety factor associated with wind turbine rotor blade fatigue loading that is not due to gravity. The method includes determining a gravity-corrected design load for wind turbine rotor blade deflection, that is determined based on the selected gravity load safety factor and the defined wind load safety factor. The method includes designing a gravity-corrected wind turbine rotor blade in accordance with the determined gravity-corrected design load.

Abstract: The present invention relates to blade monitoring of a wind turbine by actively promoting blade vibrations by imposing a pitch actuation signal. A method of operating a wind turbine is disclosed where for each blade of a wind turbine, vibrations of the blade are actively promoted by imposing a pitch actuation signal to the pitch actuator, and at least one parameter relating to the blade vibration is determined.

Abstract: A method of designing a wind turbine rotor blade. The method includes selecting a gravity load safety factor associated with wind turbine rotor blade fatigue loading due to gravity, that is selected to be less than a defined wind load safety factor associated with wind turbine rotor blade fatigue loading that is not due to gravity. The method includes determining a gravity-corrected design load for wind turbine rotor blade deflection, that is determined based on the selected gravity load safety factor and the defined wind load safety factor. The method includes designing a gravity-corrected wind turbine rotor blade in accordance with the determined gravity-corrected design load.

Abstract: The present invention provides a method of estimating an orientation of a wind turbine. The method comprises determining, using a polarising light compass of the wind turbine, a sun polarisation value, and determining a yaw angle of the wind turbine associated with the sun polarisation value. A sun direction vector is determined based on the sun polarisation value and the associated yaw angle; and an orientation of the wind turbine is estimated relative to a fixed direction using the sun direction vector.