Techniques for controlling rotor speed of a wind turbine. One technique includes defining a system model describing resonance dynamics of a wind turbine component, such as a wind turbine tower, where the system model has a nonlinear input term, e.g. a periodic forcing term. A transform is applied to the system model to obtain a transformed model for response oscillation amplitude of the wind turbine component, where the transformed model has a linear input term. A wind turbine model describing dynamics of the wind turbine is then defined, and includes the transformed model. A model-based control algorithm, e.g. model predictive control, is applied using the wind turbine model to determine at least one control output, e.g. generator torque, and the control output is used to control rotor speed of the wind turbine.

A method and a device for dampening movement in a multiple rotor (MR) wind turbine located at sea and comprising a tower (2) extending in an upwards direction, a load carrying structure (3, 4) forming a first section (3) and a second section (4), the first and second sections extending in different directions away from the tower (2). To provide efficient dampening of the movement, the method comprises tethering a first body (20) to the first section (3), the first body being at least partly submerged into the sea.

The method according to the invention for operating a wind turbine, comprising a tower and a rotor arranged at the top of the tower and having at least one rotor blade, which can be adjusted about a blade setting axis, has a first operating mode in which the at least one rotor blade has an operating angular position about the blade setting axis and a wind-force-dependent rotation of the rotor is converted into electrical power using a generator unit, which power is delivered from the wind turbine into an electrical network and/or stored, and a second operating mode in which the at least one rotor blade is adjusted by at least 60° and/or max. 110° about the blade setting axis relative to the operating angular position into a damping angular position, and a counter torque braking the rotor is controlled based on a vibration of the tower.

A method for constrained control of a wind turbine includes receiving a plurality of operating parameters corresponding to the wind turbine. The plurality of operating parameters includes a wind preview parameter and a plurality of constraint parameters. The method further includes generating a constraint parameter estimate corresponding to a future time instant for at least one constraint parameter of the plurality of constraint parameters based on the plurality of operating parameters and a wind preview model. The method also includes predicting an extreme event corresponding to the at least one constraint parameter based on the constraint parameter estimate. The method includes determining a control parameter value corresponding to a wind turbine control parameter among a plurality of wind turbine control parameters. The method also includes operating the wind turbine using a feedforward control technique based on the control parameter value to circumvent the extreme event.

The invention provides a method of controlling operation of a wind turbine having a tower. The method includes determining an overall control output including lateral oscillation control for dampening lateral oscillation of the tower, and using the overall control output to control wind turbine operation. The method further includes receiving lateral oscillation sensor data indicative of a level of lateral oscillation of the tower, determining a rated lateral oscillation control output in dependence on the received lateral oscillation data, and receiving an indication of yaw error of the wind turbine. A lateral oscillation control output included in the overall control output is determined to be de-rated from the rated lateral oscillation control output when the indicated yaw error is above a predetermined lower threshold level.

A method is provided for reducing the noise emission of a wind turbine rotor blade. The rotor blade has a leading edge, a trailing edge, a suction side, a pressure side and an attachment part at least partially on the pressure side. A pressure-side transition is present between the pressure side and the attachment part. The pressure-side transition is leveled by applying a leveling compound.

A radiating component of the wind turbine is modelled as a plurality of elements, wherein each element represents a physical portion of the radiating component and at least a portion of each of the elements are acoustically coupled to one or more of the other elements. A simulation of a vibrational source located within the wind turbine is applied at an interface of the modelled radiating component. A transfer function is used to determine the transmission of vibrations from an interface with the vibrational source to the elements. Tonal noise radiated from the elements to an environment external to the wind turbine is determined based upon the transmission of vibrations from the interface through the elements. The design of the radiating component, or of a component between the radiating component and the vibrational source, is modified to reduce the tonal noise radiated from the radiating component.

A method and an apparatus for controlling noise of multiple wind turbines. The method includes: determining a noise-influencing sector of each of the multiple wind turbines, based on positions of the multiple wind turbines and a position of a noise-influencing site; acquiring a current wind direction; determining whether there is at least one wind turbine of the multiple wind turbine under the current wind direction operating in the noise-influencing sector; and limiting output power of the at least one wind turbine, in a case that the determination is positive.

A blade pitch controller for a wind turbine includes a nominal control system and a tower feedback loop. The tower feedback loop includes a filtering system. The filtering system is arranged to control wind turbine blade pitch so as to provide additional effective stiffness to the wind turbine in response to motion of the wind turbine which is above a filter frequency of the filtering system.

A wind turbine comprising: a tower; a first arm extending from the tower; a first rotor-nacelle assembly disposed on the first arm; a first movement sensor disposed on the first arm or on the first rotor-nacelle assembly and arranged to generate first movement data based on movement of the first arm or of the first rotor-nacelle assembly; a second arm extending from the tower; a second rotor-nacelle assembly disposed on the second arm; a second movement sensor disposed on the second arm or on the second rotor-nacelle assembly and arranged to generate second movement data based on movement of the second arm or of the second rotor-nacelle assembly; and a control system coupled to the first and the second movement sensors and arranged to receive and to process the first and second movement data; wherein the control system is arranged to determine an oscillation characteristic of the wind turbine from the first and the second movement data.