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 for determining a total mechanical load of a wind turbine is provided. A present load signal indicative of a present load of a wind turbine base structure is obtained, wherein the present load acts in a present angular direction. A first present load and a second present load are derived based upon the present load signal and the present angular direction, wherein the first present load is associated with a first angular sector of the turbine and the second present load is associated with a second angular sector of the turbine. Further, a total mechanical load is derived based upon the first present load and the second present load.

Abstract: A method of controlling the load of a wind turbine is provided. A rate of wear experienced by the wind turbine as a result of the current operating conditions of the wind turbine is determined. A control vector for controlling the wind turbine is determined based on the determined rate of wear. The load of the wind turbine is controlled in accordance with the determined control vector. Determining the control vector includes weighting the determined rate of wear by a cost of electricity value and determining the control vector based on the weighted rate of wear.

Abstract: A method for controlling a wind turbine with a rotor and at least one rotor blade, and a control unit are disclosed. The method is characterised in adjusting a pitch angle of the rotor blade and determining the limit of an input value based on the adjusted pitch angle, wherein the input value includes information about the turbine rotational speed.

Abstract: A method for detecting changes in a building structure of a first wind turbine is provided. A reference value representing the eigenfrequency of the first wind turbine is monitored over time, whereby substantial changes in the reference value are used as an indication of changes in the building structure. Further, a detection assembly for such detections is provided.

Abstract: A method for operating a wind turbine is provided. At least one temperature information indicating the temperature of at least one component of the wind turbine is generated. The temperature information is used for determining at least one material property information indicating at least one component specific, temperature dependent mechanical property of the respective component. At least one operational parameter of the wind turbine is adjusted in consideration of the at least one material property information.

Abstract: A method for determining a total mechanical load of a wind turbine is provided. A present load signal indicative of a present load of a wind turbine base structure is obtained, wherein the present load acts in a present angular direction. A first present load and a second present load are derived based upon the present load signal and the present angular direction, wherein the first present load is associated with a first angular sector of the turbine and the second present load is associated with a second angular sector of the turbine. Further, a total mechanical load is derived based upon the first present load and the second present load.

Abstract: A thermal energy storage and recovery system including a storage arrangement having a thermal energy storage device for temporarily storing thermal energy, a charging/discharging arrangement having a fluid energy machine for exchanging mechanical work with a working fluid cycling through the charging/discharging arrangement, and a heat exchanger which is arranged between the storage arrangement and the charging/discharging arrangement and which thermodynamically couples a heat transfer fluid cycling through the storage arrangement with the working fluid is provided. The storage arrangement is configured in such a manner that the heat transfer fluid is under a first pressure and the charging/discharging arrangement is configured in such a manner that the working fluid is at least partially under a second pressure, wherein the second pressure is higher than the first pressure.

Abstract: A method for determining a mass change at a rotating blade of a wind turbine is provided. The method includes measuring a vibration quantity representative of a vibration of the wind turbine, measuring an azimuthal quantity representative of a rotation angle of the blade, determining a frequency quantity representative of a vibration frequency of the blade from the vibration quantity and the azimuthal quantity, and determining the mass change at the blade based on the frequency quantity.

Abstract: A method of optimising a construction of a basis of a wind turbine is provided. A local load environment situation of a construction location is analysed, which results in local load-relevant environment data, based on which construction instructions are generated. These are further based on a set of predefined rules for processing the local load-relevant environment data, such that in a first selected region of the basis along a circumference of the tower and/or in a first selected region of the foundation the carrying structure of the basis is weakened in at least one selected horizontal cross-section with respect to possible maximum loads in comparison with a second region of the basis in the selected cross-section.

Abstract: The present invention describes a blade for a wind turbine. The blade includes a heating mat for generating heat by resistive heating, wherein the heating mat is mounted to the blade. The heating mat includes a first heating power emitting section for emitting a first heating power and a second heating power emitting section for emitting a second heating power. The heating mat is coupleable to a power supply unit for transferring power to the heating mat in such a way that the first heating power differs to the second heating power.

Abstract: A method for detecting changes in a building structure of a first wind turbine is provided. A reference value representing the eigenfrequency of the first wind turbine is monitored over time, whereby substantial changes in the reference value are used as an indication of changes in the building structure. Further, a detection assembly for such detections is provided.

Abstract: An electric generator for a wind turbine, a wind turbine including such an electric generator and a method of driving such a wind turbine are provided. The electric generator includes a generator rotor and a generator stator concentrically arranged around a generator axis and at a distance from each other. The electric generator further includes a distance sensor arrangement including at least one distance sensor adapted to sense the distance between the generator rotor and the generator stator and to provide a sensor signal including an information about the sensed distance.

Abstract: A system for determining a vibrational frequency of a blade being attached to a structural component of a wind turbine is described. The blade is vibrating within a rotational plane of the rotor. A sensor sensitive to a movement along a sensor direction is placed at the structural component so the sensor direction and the direction of the longitudinal extension of the blade have a fixed angular relationship with respect to each other. The sensor is configured to provide a sensor output signal being indicative for the movement of the structural component along the sensor direction. A data processing unit is connected with the sensor and configured to determine the vibrational frequency of the blade based on the sensor output signal and on the fixed angular relationship. Corresponding wind turbine equipped with such a system, method for determining a vibrational frequency of a blade and computer program are provided.

Abstract: A method of determining a mass condition of a rotor of a wind turbine is disclosed. The method includes initiating a change of a quantity value of a quantity acting on the rotor, measuring a change of another quantity value of another quantity representative of a momentum of the rotor during a time interval, and determining the mass condition of the rotor based on the determined change of the another quantity value in relation with the initiated change of the quantity value.

Abstract: A method of determining a common blade frequency of a rotor of a wind turbine is provided. The method includes measuring a vibration quantity representative of a vibration of a component of the wind turbine, and determining the common blade frequency based the measured vibration quantity.

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.