Abstract: The invention provides a controller for a wind turbine having three rotor blades, the controller being for controlling activation of individual pitch control of the rotor blades. The controller is configured to receive a flap load signal, from a flap loading sensor of each of the three rotor blades, indicative of flap loading on each of the respective rotor blades. The controller is configured to determine, based on the received flap load signals, a statistical dispersion parameter of flap loading for each of the rotor blades, the statistical dispersion parameters being indicative of a wind event in a wind field in which the wind turbine operates. The controller is configured to control activation of individual pitch control based on the respective statistical dispersion parameters.

Abstract: A method for controlling a wind turbine to decrease blade deflection during tower passage is disclosed. A blade flap moment of the wind turbine blades is measured. A blade flap moment of the wind turbine blades and a rotor tilt moment in a situation where the pitch offset has not been added are estimated, based on the measured blade flap moment. In the case that the estimated blade flap moment exceeds a first activation threshold value and the estimated rotor tilt moment exceeds a second activation threshold value, individual pitch angle adjustment of the wind turbine blades is initiated by adding a pitch offset, at azimuth angles within an azimuth adjustment region corresponding to tower passage of the wind turbine blades.

Abstract: Adjusting pitch of the wind turbine rotor blades to reduce fatigue of the wind turbine tower. Flap loading sensor data is received for the rotor blades, and a flap loading vector in a rotor coordinate frame of the wind turbine is obtained. The flap loading vector is transformed to obtain first and second mutually orthogonal components in a fixed wind turbine coordinate frame, and respective 3P (blade passing frequency) components in the fixed frame indicative of 3P frequency content of the wind turbine tower are determined. A control action is applied to obtain respective 3P control components for mitigating the 3P frequency content of the tower, an inverse transform is applied to the 3P control components to obtain pitch reference offset values for the respective rotor blades in the rotor coordinate frame, and blade pitch is adjusted based on the pitch reference offset values.

Abstract: The invention relates to adjusting pitch of rotor blades of a wind turbine. An acceleration signal is received from a wind turbine acceleration sensor and is indicative of side-to-side motion of the wind turbine tower. A first component in a fixed coordinate frame of the wind turbine is determined based on the received acceleration signal. The first component is indicative of a whirling mode of the wind turbine caused by edgewise vibrations of the rotor blades. A second component is generated based on the first component and is orthogonal to the first component. A control action is applied to obtain first and second control components for mitigating the whirling mode. An inverse m-blade coordinate transformation is applied to the first and second control components to obtain pitch reference offset values in a rotor coordinate frame of the wind turbine, which are used to adjust pitch of the rotor blades.

Abstract: A method of damping motion of a wind turbine, the wind turbine comprising a rotor and a floating platform. A motion signal is generated which is indicative of a motion of the wind turbine. A wind direction signal is generated which is indicative of a wind direction relative to the floating platform. A damping signal is generated on the basis of the motion signal and the wind direction signal, and the motion of the wind turbine is damped on the basis of the damping signal, for instance by adjusting the pitch of the rotor blades. A phase of the damping signal may be controlled on the basis of the wind direction signal.

Abstract: The present invention relates to pitch actuation of pitch-adjustable rotor blades of a three-bladed wind turbine in a situation where one blade load sensor is unavailable. Based on blade load signals and an availability signal for each of the blade load signals, combined load signals are constructed based on the available blade load signals. The combined load signals are determined based on application of a high pass filter to the blade load signals and a transform of the blade load signals to an intermediate coordinate frame, wherein, in the transform, the unavailable blade load signal is replaced with an estimated signal. A control action is performed using the combined load signals, and the resulting pitch modification signals are applied to the pitch actuator.

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.