The present disclosure relates to a method of operating a wind turbine, a corresponding wind turbine, a method of controlling a wind farm and a corresponding wind farm. The method comprises the steps of: determining a target maximum active power to be fed by the wind turbine into a power grid, in particular into an electricity power grid; monitoring a current active power fed from the wind turbine into the power grid; determining a reference time period corresponding to the determined target maximum active power; deriving an average of the active power fed from the wind turbine into the power grid during the reference time period; comparing the average of the active power with the target maximum active power; and operating the wind turbine at a set operating point permitting active power above the target maximum active power in case the average of the active power is below the target maximum active power.

Method for controlling a rotor speed of a rotor of a wind turbine at rated or curtailed operation conditions the rotor being an aerodynamic rotor having one or a plurality of rotor blades, and the wind turbine further having a tower and a generator wherein a pitch control provides a pitch angle set value depending on an actual rotor speed for setting a pitch angle of the rotor blades, a main control provides a main power or torque set value for controlling the power or torque of the generator, and an additional control provides an additional power or torque set value depending on the actual rotor speed , wherein the additional power or torque set value is provided as an offset value and is added to the main power or torque set value respectively, wherein the additional power or torque set value is calculated depending on a control deviation of the rotor speed, and optionally, in combination with the additional control, or instead of it, a maximum power control provides a maximum power value as a varying value for limiting an output power of the generator and the maximum power value is calculated depending on a predetermined power limit value, and depending on a predetermined reference duration, in order to provide for the reference duration an average power reaching or at least not exceeding the predetermined power limit value.

A method for operating a wind turbine for generating electrical power from wind, wherein the wind turbine has an aerodynamic rotor with a rotor hub and rotor blades of which the blade angle is adjustable, and the aerodynamic rotor can be operated with a variable rotation speed, and the wind turbine has a generator, which is coupled to the aerodynamic rotor, for the purpose of generating a generator power, wherein the generator can be operated with a variable generator torque, comprising the steps of: determining a loading variable which indicates a loading on the wind turbine by the wind, and reducing the rotation speed and/or the generator power in a loading mode depending on the loading variable, wherein at least one force variable that acts on the wind turbine is used for determining the loading variable or as the loading variable.

A method of controlling a wind turbine for the avoidance of edgewise vibrations. The method comprises the steps of determining a whirling mode frequency of a rotor blade of the wind turbine; determining a rotational frequency of the rotor blade corresponding to the speed of the rotor blade; determining a threshold value for the whirling mode frequency based on the rotational frequency; and, reducing the speed of the rotor blade if the whirling mode frequency substantially equals or is less than the threshold value.

The present invention relates to a method and a system for tracking the motion of a blade of a wind turbine. One embodiment relates to a blade motion tracking system for installation on a wind turbine blade, where the wind turbine blade comprises a blade root and a blade tip. The system comprises at least one light module comprising at least a first light source, preferably adapted to emit light in the direction of the blade root. An optical measuring device is provided, preferably located at the blade root, adapted to receive light emitted from the first light source(s). The optical measuring device is preferably a position sensitive detector identifying the position of the first light source relative to the position sensitive detector. A single light source located at the tip of the blade, close to the tip of the or towards the tip of the blade, is sufficient to measure deflection of the blade. Advantageously the first light source is modulated with a predefined modulation frequency such that light from the first light source can be distinguished from ambient light and thereby minimize the influence of the ambient light conditions during detection.

A method of controlling pitch of individual blades in a wind turbine is described, together with a suitable controller. Wind speed is determined as a function of azimuthal angle. Wind speed is then predicted for individual blades over a prediction horizon using this determination of wind speed as a function of azimuthal angle. The predicted wind speed for each individual blade is used in a performance function, which is optimized to control individual blade pitches.

Provided is a control device configured to control a wind turbine, the wind turbine including a rotor being rotatable about a rotational axis, wherein the rotor has at least one blade, the blade including at least one add-on member which is actuated by a corresponding trim actuator to alter aerodynamic properties of the blade and a pitch actuator to alter a pitch angle of the blade. The control device is configured to determine an idling mode or a self-sustaining mode of the wind turbine; to control the pitch actuator to set a predetermined pitch angle of the blade, if the idling mode or the self-sustaining mode is determined; and to cause a target rotational speed of the rotor by variably controlling the trim actuator of the blade, if the idling mode or the self-sustaining mode is determined.

The present invention describes a wind turbine comprising a hub, at least one blade and at least one pitch bearing to connect the at least one blade to the hub, the at least one pitch bearing comprising at least an inner ring and an outer ring, and at least a rolling race, wherein the wind turbine further comprises at least a tensioning system configured to exert a radial compression force to at least a part of the outer ring of the at least one pitch bearing, thus increasing the resultant stiffness of the at least one pitch bearing.

A controller is provided for a floating wind turbine including a rotor with a number of rotor blades connected to a generator. The controller includes an active damping controller for calculating one or more outputs for damping both a first motion of the floating wind turbine in a first frequency range and a second motion of the floating wind turbine in a second frequency range based on an input of the first motion and an input of the second motion, The controller is arranged to calculate an output for controlling a blade pitch of one or more of the rotor blades and/or for controlling a torque of the generator based on an actual rotor speed, a target rotor speed, and the one or more outputs from the active damping controller such that both the first motion and the second motion will be damped.

A bearing protection arrangement of a journal bearing arranged between a housing and a rotary component of a wind turbine. The bearing protection arrangement includes a wind speed monitor arranged to monitor wind speed in the vicinity of the wind turbine and to generate a wake-up signal when the wind speed exceeds a pre-defined minimum; a mode switch module of a backup battery arranged to provide restart power to an auxiliary of the wind turbine, which mode switch module is adapted to switch the backup battery from a normal-power mode into a low-power mode to conserve sufficient restart power after low wind-speed conditions, and to switch the backup battery from the low-power mode into a normal-power mode in response to the wake-up signal. A wind turbine and a method of protecting a journal bearing of a wind turbine during standstill.