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 comprising a plurality of position detection components each collecting data regarding a field of detection through which a segment of the turbine blades passes, wherein the position detection components are monitoring distinct fields of detection to collect distances of a plurality of segments of each one of the turbine blades travelling through the fields of detection. The system further comprises a deflection controller configured to receive the collected distances and to determine deflection of the turbine blades accordingly. An associated method comprises collecting distances of a plurality of distinct segments of the turbine blades when the turbine blades travel within a plurality of fields of detections, and processing the collected distances to determine clearance between the turbine blades and the tower.

A wind turbine blade comprising a system for monitoring the deflection of a wind turbine blade is described. The system comprises a wireless range-measurement system, having at least one wireless communication device located towards the root end of the blade and at least one wireless communication device located towards the tip end of the blade, the communication devices comprising antennas polarized substantially perpendicular to the suction side of the blade and substantially parallel to the leading edge of the wind turbine blade.

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 invention relates to a method for controlling a wind turbine, in particular a method for controlling pitch of one or more blades of a wind turbine and related system. The method comprises collecting first data indicative of a dynamic condition of the first wind turbine blade and the rotor, the first data comprising rotor data and first deflection data, the rotor data being indicative of the azimuth position and rotational velocity of the rotor in a rotor plane perpendicular to the rotor axis, and the first deflection data being indicative of the position, speed and acceleration of one or more parts of the first wind turbine blade. Further, the method comprises calculating an expected tower clearance distance at a later time of tower passage for the first wind turbine blade based on the first data including acceleration of one or more parts of the first wind turbine blade, and performing measures to prevent tower collision, if the expected tower clearance distance fulfills a collision risk criterion.

A method of determining a distance between a rotor blade tip and a tower of a wind turbine includes: estimating the distance based on a strain measurement; measuring the distance; correcting an estimation procedure based on the estimated distance and the measured distance; and deriving a corrected distance based on the corrected estimation procedure.

In a wind turbine of the type including a tower and a nacelle with the rotor being rotatably connected to the nacelle for rotating about a rotor axis and having a plurality of equally spaced blades, there is provided a method of detecting damage to a rotor requiring replacement. The method includes positioning video cameras on each of the blades at a root of a respective one of the blades so as to provide a line of sight of the camera along the respective one of the blades to the tip to obtain a video image of the rotor and tip as they rotate. From the videos an analysis is carried out of the images of the tip at a common location spaced away from the tower to determine a position of the tip and hence the deflection of the tip which is indicative of damage.

A system for monitoring the deflection of a wind turbine blade is described. The system comprises a wireless range-measurement system, having at least one wireless communication device located towards the root end of the blade and at least one wireless communication device located towards the tip end of the blade. The root end device is provided on a bracket projecting from the external surface of the blade, to provide a communication path between the root end and tip end devices which is less susceptible to interference from multipath effects, etc. There is further provided a method to derive tilt and yaw moments from measured deflections. A control method for such a system is also described, wherein the signal gain of the communication path may be varied based at least in part upon the deflection characteristics of the wind turbine blade.

A method for controlling a wind turbine, and an associated wind turbine, includes receiving a wind direction signal indicative of an instantaneous wind direction at the wind turbine and receiving a signal indicative of an instantaneous wind speed at the wind turbine. A rate of change of the wind direction at the wind turbine and a rate of change of wind speed at the wind turbine are determined. A control signal for a pitch system for blades of the wind turbine is determined based on the rate of change of the wind direction and the rate of change of wind speed. The pitch of the blades is then changed with the pitch system based on the control signal to reduce loads on the wind turbine from changes in the wind direction simultaneous with changes in the wind speed.

A wind turbine blade comprising a system for monitoring the deflection of a wind turbine blade is described. The system comprises a wireless range-measurement system, having at least one wireless communication device located towards the root end of the blade and at least one wireless communication device located towards the tip end of the blade, the communication devices comprising antennas polarized substantially perpendicular to the suction side of the blade and substantially parallel to the leading edge of the wind turbine blade.

A method of calibrating a load measurement apparatus for measuring a load on a wind turbine blade on the basis of strain data based on strain of a wind turbine blade includes: a strain-data acquisition step of, during a startup of a wind turbine, obtaining a plurality of the strain data for each of a plurality of conditions among which at least one of an azimuth angle or a pitch angle of the wind turbine blade is different from one another; a theoretical load-value acquisition step of obtaining a theoretical load value applied to the wind turbine blade due to own weight of the wind turbine blade, for each of the plurality of conditions, on the basis of the azimuth angle and the pitch angle of the wind turbine blade in each of the plurality of conditions; and a calibration-parameter calculation step of calculating a calibration parameter representing a relationship between the strain data obtained by the load measurement apparatus and the load on the wind turbine blade, on the basis of a correlation between each of the strain data and the theoretical load value.