The invention relates to a method of determining a tip-to-tower clearance of a wind turbine, the wind turbine comprising a wind turbine tower, where a distance sensor unit is arranged on at least one wind turbine blade of the wind turbine and comprises at least a transmitter and a receiver, wherein the method comprises the steps of: transmitting a signal from the distance sensor unit toward the wind turbine tower, measuring a signal reflected from the wind turbine tower, determining a distance between the wind turbine tower and the at least one wind turbine blade based on the transmitted signal and the reflected signal, wherein the method further comprises the step of correcting the measured distance based on at least one of an actual pitch angle and a deflection angle of the at least one wind turbine blade at the location of the distance sensor unit.

A method for controlling pitching of at least one rotor blade of a wind turbine includes receiving, via one or more position localization sensors, position data relating to the at least one rotor blade of the wind turbine. Further, the method includes determining, via a controller, a blade deflection signal of the at least one rotor blade based on the position data. Moreover, the method includes determining, via a computer-implemented model stored in the controller, a pitch command for the at least one rotor blade as a function of the blade deflection signal and an azimuth angle of the at least one rotor blade.

In a wind turbine comprising a tower supporting a nacelle, at least one blade rotationally attached to the nacelle and having a blade-tip section, a system for measuring the separation distance between the tower and the blade-tip-section of the wind turbine, comprising an indicator stripe on the surface of the blade-tip section, an indicator ring encircling the tower, a camera in the nacelle and positioned such that the blade-tip section and the indicator ring are within the camera's field of view when the blade-tip is at its closest approach position to the tower, the camera digitally recording an image of its field of view at this closest approach position, the distance between indicator ring and camera being essentially equal to the distance between the indicator stripe and the camera at this closest approach position, and an image processor and tip-tower clearance calculator unit receiving the digitally recorded image and calculating a physical separation distance between the indicator stripe and the indicator ring using the digitally recorded image information, the physical separation distance being indicative of the blade tip-tower clearance.

A structure adapted to traverse a fluid environment exerting an ambient fluid pressure is provided. The structure includes an elongate body extending from a root to a wingtip and encapsulating at least one interior volume containing an interior fluid exerting an interior fluid pressure that is different from the ambient fluid pressure. A method of retrofitting a structure adapted to traverse a fluid environment exerting an ambient fluid pressure, the structure comprising an elongate body extending from a root to a wingtip and having at least one interior volume is also provided. The method includes sealing the elongate body to encapsulate the at least one interior volume containing an interior fluid; associating at least one valve with the at least one interior volume; and modifying interior fluid content via the at least one valve to produce an interior fluid pressure that is different from the ambient fluid pressure.

The present disclosure relates to methods and systems for measuring deflection of blades of a wind turbine. Examples include a light emitting and collection device mounted to the nacelle and configured to emit light in a direction within a substantially vertical plane. Examples include a method for operating a wind turbine including emitting light above a hub, receiving the light when reflected by a blade of the wind turbine, and, if the level of blade deflection is above a threshold, reducing blade loading of the blade before the blade reaches a vertically downward position. Examples include a method for monitoring deflection of a rotor blade of a wind turbine comprising emitting a light sheet, collecting reflections of the emitted light, and determining deflection of the rotor blade by determining a time during which the blade reflects the emitted light sheet.

An upwind wind turbine comprising a tower and a rotor is described. The wind turbine additionally includes a pressure-sensing device supported by the tower at a location within the wake of the rotor. The pressure-sensing device is configured to sense air pressure and provide a signal indicative of the sensed air pressure to a wind turbine controller for use in controlling the rotor of the wind turbine.

A method for the calculation of a wind turbine blade deflection is described. The method utilises a known blade modal profile in the calculation of the blade deflection, such that the a priori knowledge of the blade excitation modes can be used with a simple distance measurement to determine the blade deflection shape. The calculated blade deflection can then be used as an input to control wind turbine operation, e.g. where it is likely that the deflected blade might result in a tower strike.

A method of determining a blade clearance during operation of a wind turbine is provided, the blade clearance corresponding to a distance between a rotor blade and a tower of the wind turbine. The method includes (a) detecting a rotor blade velocity, (b) emitting a first signal from an observer location, the first signal having a first frequency, (c) receiving a second signal at the observer location, the second signal being reflected from the rotor blade when the first signal impinges on the rotor blade, (d) determining a Doppler shift of the second signal relative to the first signal, and (e) determining the blade clearance based on the first frequency, the Doppler shift, the observer location, and the rotor blade velocity, wherein the step of determining the blade clearance utilizes a mathematical model. A corre-sponding system and a wind turbine comprising such a system are also provided.

Described is a system for monitoring deflection of turbine blades of a wind turbine comprising a tower. The system comprises a position detecting apparatus mounted to the wind turbine, the position detection apparatus comprising position detection components each detecting a presence or absence of a corresponding one of the segments of the turbine blades; and a deflection controller configured to receive the presence or absence detection and to use the presence or absence detection to determine a distance of each of the segments of the turbine blades relative to the tower, whereby the distance of each of the segments of the turbine blades relative to the tower is representative of the deflection of the turbine blades.

The present disclosure relates to methods and systems for measuring deflection of blades of a wind turbine. Examples include a light emitting and collection device mounted to the nacelle and configured to emit light in a direction within a substantially vertical plane. Examples include a method for operating a wind turbine including emitting light above a hub, receiving the light when reflected by a blade of the wind turbine, and, if the level of blade deflection is above a threshold, reducing blade loading of the blade before the blade reaches a vertically downward position. Examples include a method for monitoring deflection of a rotor blade of a wind turbine comprising emitting a light sheet, collecting reflections of the emitted light, and determining deflection of the rotor blade by determining a time during which the blade reflects the emitted light sheet.