Abstract: A method for operating a wind turbine which includes a rotor hub supporting a rotor blade includes: a) detecting changes in the aerodynamic performance of the rotor blade; b) determining a first control rule; c) determining a first power output information indicating a first power output based on the first control rule; d) changing an operational parameter and choosing a second control rule such that the first control rule is replaced by the second control rule; e) determining a second power output information indicating a second power output based on the second control rule. c) comparing the first and second power output information. If the second power output exceeds the first power output, repeating a)-f) with the second control rule being used as the first control rule in b); otherwise repeating a)-f) a different second control rule is applied in d).

Abstract: A method and a control device for damping an oscillatory movement of the top of a tower of a wind turbine are provided. The described method includes (a) rotating a rotor being rotatably attached to a nacelle of the wind turbine with a rotational speed, and (b) yawing the nacelle of the wind turbine around an axis being aligned with the longitudinal axis of the tower with a yawing speed. Thereby, a yawing movement being associated with yawing the nacelle is coordinated with the oscillatory movement in such a manner that a gyroscopic torque resulting (i) from rotating the rotor and (ii) from yawing the rotor damps the oscillatory movement of the top of the tower. A wind turbine comprising such a control device and a computer program for controlling this method are also provided.

Abstract: A method for controlling a generator having a rotor with a plurality of magnets and a first stator winding and a second stator winding, electrically separate from the first stator winding is provided. The rotor rotates around a rotation axis perpendicular to a radial direction relative to the stator windings. The method includes allowing flow of a first electric current through the first stator winding, thereby generating a first radial force having a first magnitude and acting between the first stator winding and the rotor, and allowing flow of a second electric current through the second stator winding, thereby generating a second radial force having a second magnitude and acting between the second stator winding and the rotor, wherein the first magnitude is different from the second magnitude resulting in a net generator generated radial force generated by the first stator winding and the second stator winding at the rotor.

Abstract: A method is provided for controlling the pitch systems of a plurality of pitch systems of a wind turbine. The method includes generating a main pitch control signal for the pitch systems on the basis of a performance parameter of the wind turbine and generating a distinct auxiliary pitch control signal for each individual pitch system of the plurality of pitch systems. The method further includes adding an auxiliary pitch control signal to the main pitch control signal to give a combined pitch control signal for a pitch system. The method then includes controlling that pitch system in response to that combined pitch control signal wherein an auxiliary pitch control signal is suppressed when a pitch activity value and/or a pitch variation value is below a predefined threshold.

Abstract: A stall sensor for a wind turbine is provided. A wind turbine including such a stall sensor and a method of operating such a wind turbine are also provided. The stall sensor includes detector means adapted to measure vibration of a rotor blade of the wind turbine and to output a vibration signal representative of the vibration of the rotor blade, conversion means connected to the detector means and adapted to determine a noise figure representative of a spectral signal content within a frequency band of the vibration signal received from the detector means and arbiter means connected to the conversion means and adapted to signal a presence or an absence of stall based on the noise figure received from the conversion means.

Abstract: A method for controlling a generator having a rotor with a plurality of magnets and a first stator winding and a second stator winding, electrically separate from the first stator winding is provided. The rotor rotates around a rotation axis perpendicular to a radial direction relative to the stator windings. The method includes allowing flow of a first electric current through the first stator winding, thereby generating a first radial force having a first magnitude and acting between the first stator winding and the rotor, and allowing flow of a second electric current through the second stator winding, thereby generating a second radial force having a second magnitude and acting between the second stator winding and the rotor, wherein the first magnitude is different from the second magnitude resulting in a net generator generated radial force generated by the first stator winding and the second stator winding at the rotor.

Abstract: A method for operating a wind turbine which includes a rotor hub supporting a rotor blade is disclosed. The method includes: a) detecting changes in the aerodynamic performance of the rotor blade; b) determining a first control rule; c) determining a first power output information indicating a first power output based on the first control rule; d) changing an operational parameter and choosing a second control rule such that the first control rule is replaced by the second control rule; e) determining a second power output information indicating a second power output based on the second control rule. c) comparing the first and second power output information. If the second power output exceeds the first power output, repeating a)-f) with the second control rule being used as the first control rule in b); otherwise repeating a)-f), whereby a different second control rule is applied in d).

Abstract: A method for operating a wind turbine is proposed. The wind turbine has a rotor, a wind turbine converter and a wind turbine output terminal connected to a utility grid. The converter has a converter output terminal upstream of the wind turbine output terminal. An input signal related to an action output of the wind turbine is obtained at a location between the rotor and the wind turbine output terminal. A power difference is estimated between the power associated with the action output at the location and the output power at the converter output terminal. The converter is controlled based on the input signal and the estimated power difference.

Abstract: A method to control the operation of a wind turbine above a wind speed threshold value and a wind turbine designed to execute the method are provided. Electrical output power of the wind turbine is produced by its rotating blades and fed into a grid, which is connected with the wind turbine. The wind turbine is controlled by a first control loop and a second control loop. The wind speed is determined and compared with a certain predefined wind speed threshold value. Wind turbulences are determined and compared with a predefined wind turbulence threshold value. The first control loop and the second control loop are activated when the wind speed reaches or exceeds the wind speed threshold value. The activated first control loop controls the output power dependent on the wind speed. The activated second control loop controls the rotational speed of the rotating blades dependent on the wind turbulences.

Abstract: It is described an arrangement for determining a target value of an operational variable of a wind turbine, the arrangement comprising: at least one input terminal for receiving at least one operational parameter of the wind turbine; a determining unit adapted to determine a target value of an operational variable of the wind turbine based on the operational parameter. Further, a corresponding method and a wind turbine are described.

Abstract: A method of controlling a wind turbine is provided. The method includes the steps of obtaining a number of operating values relevant to a wind turbine, calculating a thrust setpoint on the basis of the operating values, and controlling a wind turbine according to a thrust setpoint. A wind park controller, a wind turbine controller, and a wind park are also provided.

Abstract: A method for lubricating at least one blade pitch bearing of a wind turbine is provided. The wind turbine includes a rotor hub with a number of rotor blades, with each rotor blade being supported to the rotor hub by at least one blade pitch bearing. At least one rotor blade is pitchable and a rotor blade pitch control device adapted to control pitching of the at least one rotor blade. The state of lubrication of at least one blade pitch bearing by a lubrication detection device generating at least one lubrication information signal indicating a degree of lubrication of the at least one blade pitch bearing by measuring the electrical capacitance and/or resistance of the at least one blade pitch bearing. A rotor blade lubricating device is actuated to perform at least one action to lubricate the at least one blade pitch bearing, if the lubrication information signal indicates that the at least one blade pitch bearing is not sufficiently lubricated.

Abstract: A method for lubricating a bearing of a variable-pitch wind turbine is disclosed. The electrical capacitance and/or resistance of the bearing is measured and the state of lubrication of the bearing by is determined from the measurement. The bearing is lubricated when state of lubrication indicates that the bearing is insufficiently lubricated.

Abstract: A wind turbine rotor blade is equipped with an air chamber and equipped via the air chamber to route a modulation beam out of the rotor blade such that the air current along the rotor blade is changed. Thereby the laminar current is changed into a turbulent current on the one hand and its detachment and on the other hand its recreation is achieved in order to produce the laminar current. The control may occur via electrostatic actuators via a learnable control strategy based on neural forecasts, which take the complexity of the non-linear system into account and allow for the plurality of influencing factors. The stress on the rotor blades may be reduced, resulting in longer service life and reduced maintenance costs, a higher level of efficiency or quieter operation.

Abstract: A method and corresponding arrangement are provided for determining pitch angle adjustment signals for adjusting a pitch angle of a rotor blade connected to a rotation shaft of a wind turbine. The method includes obtaining a first maximal speed signal indicative of a first desired maximal rotational speed of the rotation shaft. The method also includes deriving a first pitch angle adjustment signal based on the first maximal speed signal. The method further includes obtaining a second maximal speed signal indicative of a second desired maximal rotational speed of the rotation shaft different from the first desired maximal rotational speed of the rotation shaft. Further, the method includes deriving a second pitch angle adjustment signal based on the second maximal speed signal. The second pitch angle adjustment signal is different from the first pitch angle adjustment signal.

Abstract: A method for determining and applying a pitch angle offset signal for controlling a rotor frequency of a rotor of a wind turbine is disclosed. The method includes obtaining a motion quantity indicative of a motion of the rotor and determining the pitch angle offset signal based on the motion quantity such that the pitch angle offset signal is adapted to be used for adjusting a blade pitch angle of a rotor blade mounted at the rotor for controlling the rotor frequency in order to reduce a time span during which the rotor is in a critical motion region. A corresponding system and a method for controlling a rotor frequency are also disclosed.

Abstract: A method is provided of determining a phase value of a phase associated with an oscillatory tower movement of a tower of a wind turbine. The method includes measuring a quantity representative of the oscillatory tower movement, and determining the phase value based on the measured quantity. In an exemplary embodiment, the determination of the phase value is includes applying a Fourier Transformation on the measured quantity.