Abstract: The present invention relates to a system and a method for optimal yaw control of a wind turbine, comprising a tower carrying a rotatable nacelle rotated by a yaw motor, which nacelle comprises at least one generator connected by a shaft to a rotor, comprising one or more wings, which nacelle further comprises means for detecting wind direction and wind velocity, which system performs measurement and storing data related to power production, wind velocity and wind direction. The object of this invention is to optimize the yaw position of a nacelle to the wind direction. The object can be fulfilled by power production measured in a positive direction to actual yaw position is accumulated in a first storages related to measured wind direction and that power production measured in a negative direction to actual yaw position is accumulated in a second storages related to measured wind direction. By this system the power production of the wind turbine is optimized by self-calibrating yaw control.

Abstract: The present invention relates to a system adapted to reduce the load of a wind turbine in situations with high yaw error or by gust ride, which system has access to at least some operational parameters. The object is to reduce the maximal load of a wind turbine in situations where wind gust hits the wind turbine. The system can monitor at least a combination of these parameters, which system by a defined combination of at least some of actual parameters performs a pitch or speed regulation in order to bring the wind turbine into a safe mode of operation and reduce the load of the wind turbine. Hereby can be achieved that the system can monitor some of existing parameters for a wind turbine in operation and through these parameters it is possible with this system to perform an analysis of critical combinations of parameter values.

Abstract: A tool for reducing vibrations in wind turbine blades at standstill includes an elongate sleeve formed of a net-like material for fitting over the blades, wherein the sleeve is formed with at least one protruding structure extending along at least a part of the length of the sleeve having an undulating form, and which is arranged so that when the sleeve is fitted on a blade the protruding structure or structures lie at the leading and/or trailing edge of the blade. A method for securing wind turbine blades against oscillations is also disclosed.

Abstract: The present invention relates to a system and a method for optimal yaw control of a wind turbine, comprising a tower carrying a rotatable nacelle rotated by a yaw motor, which nacelle comprises at least one generator connected by a shaft to a rotor, comprising one or more wings, which nacelle further comprises means for detecting wind direction and wind velocity, which system performs measurement and storing data related to power production, wind velocity and wind direction. The object of this invention is to optimize the yaw position of a nacelle to the wind direction. The object can be fulfilled by power production measured in a positive direction to actual yaw position is accumulated in a first storages related to measured wind direction and that power production measured in a negative direction to actual yaw position is accumulated in a second storages related to measured wind direction. By this system the power production of the wind turbine is optimized by self-calibrating yaw control.

Abstract: A method of estimating an amount of undesired loading experienced by at least a portion of a structure (100) is provided. The structure (100) may be, for example, a wind turbine generator (WTG) and the portion for which undesired loading is estimated may be, for example, a rotor (130) of the WTG. The method includes receiving a first signal characterizing instantaneous stress experienced by a component (140) of the structure (100) and filtering out at least a portion of the received first signal that corresponds to the desired loading experienced by the component to produce a first filtered signal. The amount of undesired loading experienced by the at least a portion of the structure (100) is estimated based at least partially on the first filtered signal.

Abstract: The invention relates to a method of controlling a wind turbine comprising one or more blades attached to a rotor hub, the one or more blades being arranged to pitch relative to the hub, the method comprising the steps of obtaining a blade load signal comprising data on an absolute load on the one or more blades; processing the blade load data to detect a high thrust wind event, and generating a control signal comprising a pitch contribution for affecting the blades to pitch out of the wind in response to the detected wind event. The invention also relates to a wind turbine, a control system for a wind turbine and a computer program product being adapted to enable a computer system to perform the method of the invention.

Abstract: A method of controlling a wind turbine comprising blades attached to a rotor hub for rotation in a rotor plane and a control system for individually pitching the blades relative to the hub. The method comprises dividing the rotor plane into a number of sectors, determining the individual sectors for each blade during the rotation by means of an azimuth angle sensor, and obtaining blade sensor data from a blade sensor on an individual blade relating to a sector, and comparing the obtained data with data relating to the same sector and representing blade sensor data on other blades. When an event is detected in a given sector, an individual pitch contribution is determined in the sector, and the blades are then pitched according to this individual pitch contribution for that given sector at least partly during passage of the sector.

Abstract: A tool for reducing vibrations in wind turbine blades at standstill includes an elongate sleeve formed of a net-like material for fitting over the blades, wherein the sleeve is formed with at least one protruding structure extending along at least a part of the length of the sleeve having an undulating form, and which is arranged so that when the sleeve is fitted on a blade the protruding structure or structures lie at the leading and/or trailing edge of the blade. A method for securing wind turbine blades against oscillations is also disclosed.

Abstract: The invention relates to a method of controlling a wind turbine comprising one or more blades attached to a rotor hub, the one or more blades being arranged to pitch relative to the hub, the method comprising the steps of obtaining a blade load signal comprising data on an absolute load on the one or more blades; processing the blade load data to detect a high thrust wind event, and generating a control signal comprising a pitch contribution for affecting the blades to pitch out of the wind in response to the detected wind event. The invention also relates to a wind turbine, a control system for a wind turbine and a computer program product being adapted to enable a computer system to perform the method of the invention.

Abstract: A method of estimating an amount of undesired loading experienced by at least a portion of a structure (100) is provided. The structure (100) may be, for example, a wind turbine generator (WTG) and the portion for which undesired loading is estimated may be, for example, a rotor (130) of the WTG. The method includes receiving a first signal characterizing instantaneous stress experienced by a component (140) of the structure (100) and filtering out at least a portion of the received first signal that corresponds to the desired loading experienced by the component to produce a first filtered signal. The amount of undesired loading experienced by the at least a portion of the structure (100) is estimated based at least partially on the first filtered signal.

Abstract: The invention relates to a method of controlling a wind turbine having a rotor with pitchable wind turbine blades and a generator for producing power, where a pitch reference value for the wind turbine blades is determined, and an operational parameter representing a loading on the wind turbine rotor exerted by the wind is measured at time intervals. A variation parameter reflecting a variation of the operational parameter over time is determined and used in the determination of a minimum pitch limit value of the pitch reference value. The wind turbine is then controlled according to the pitch reference value only if the pitch reference value is above or equal to the minimum pitch limit value, and otherwise according to the minimum pitch limit value.

Abstract: A method of controlling a wind turbine comprising blades attached to a rotor hub for rotation in a rotor plane and a control system for individually pitching the blades relative to the hub. The method comprises dividing the rotor plane into a number of sectors, determining the individual sectors for each blade during the rotation by means of an azimuth angle sensor, and obtaining blade sensor data from a blade sensor on an individual blade relating to a sector, and comparing the obtained data with data relating to the same sector and representing blade sensor data on other blades. When an event is detected in a given sector, an individual pitch contribution is determined in the sector, and the blades are then pitched according to this individual pitch contribution for that given sector at least partly during passage of the sector.

Abstract: The invention relates to a method of controlling a wind turbine having a rotor with pitchable wind turbine blades and a generator for producing power, where a pitch reference value for the wind turbine blades is determined, and an operational parameter representing a loading on the wind turbine rotor exerted by the wind is measured at time intervals. A variation parameter reflecting a variation of the operational parameter over time is determined and used in the determination of a minimum pitch limit value of the pitch reference value. The wind turbine is then controlled according to the pitch reference value only if the pitch reference value is above or equal to the minimum pitch limit value, and otherwise according to the minimum pitch limit value.

Abstract: A method for controlling a wind turbine rotor during a stop process by pitching the rotor blades fast, e.g. with an angular rate of 10-15°/s to a no-thrust position, after which the rotor blades are pitched to maintain the no-thrust or a thrust against the direction of the pendulum movement of the tower for a while to prevent the aerodynamic thrust from aggravating the pendulum movement of the tower. With this control strategy, the bending moments of the tower root are minimized, leading to avoidance of wind turbine tower failure, to prolongation of the life time for a wind turbine tower and the possibility of erecting wind turbine towers of less reinforcement at the tower root.

Abstract: A wind turbine is presented where the operation lifetime of the main bearing is extended by relieving the main bearing by reducing the mean bending moment on the bearing by means of individual pitch control of the blades of the rotor so as to create an aerodynamic mean tilt moment on the rotor by means of aerodynamic forces on the blades, the tilt moment at least partly counteracting the bending moment caused by the overhang load forces on the main bearing from the gravitational pull on the rotor mass.

Abstract: A method for controlling a wind turbine rotor during a stop process by pitching the rotor blades fast, e.g. with an angular rate of 10-15°/s to a no-thrust position, after which the rotor blades are pitched to maintain the no-thrust or a thrust against the direction of the pendulum movement of the tower for a while to prevent the aerodynamic thrust from aggravating the pendulum movement of the tower. With this control strategy, the bending moments of the tower root are minimized, leading to avoidance of wind turbine tower failure, to prolongation of the life time for a wind turbine tower and the possibility of erecting wind turbine towers of less reinforcement at the tower root.

Abstract: A wind turbine is presented where the operation lifetime of the main bearing is extended by relieving the main bearing by reducing the mean bending moment on the bearing by means of individual pitch control of the blades of the rotor so as to create an aerodynamic mean tilt moment on the rotor by means of aerodynamic forces on the blades, the tilt moment at least partly counteracting the bending moment caused by the overhang load forces on the main bearing from the gravitational pull on the rotor mass.

Abstract: The present invention relates to a wind turbine with oscillation damping means provided at the nacelle and being designed for damping edgewise oscillations of the rotor blades in the rotational plane of the rotor. In particular, the invention relates to a wind turbine in which the oscillation damping means are provided at the end of the nacelle being opposite to the end from which the rotor extends and are designed for damping oscillations of the first eigenfrequency of the rotor blades in the rotational plane, especially oscillations being perpendicular to the rotational axis of the rotor. The damping means are advantageously designed to dampen oscillations of a frequency being substantially equal to the first eigenfrequency in the rotational plane of the at least one blade minus the frequency of rotation of the rotor. The oscillation damping means of the present invention are preferably capable of damping oscillations being substantially horizontal and substantially perpendicular to the rotation axis.