A method of determining an offset angle to the wind direction measured from a wind vane of a wind turbine includes the steps of: defining a plurality of power bins representing an interval of power which can be produced by the wind turbine, calculating an efficiency of the wind turbine for a plurality of time slots, determining a power output of the wind turbine for the plurality of time slots, comparing the efficiency of the wind turbine in two different time slots, and updating a value of the one of the power bins representing the interval of power determined for one of the compared time slots. The value of the power bin is updated with the result of the highest efficiency or a value derived from the highest efficiency multiplied with a constant.

The invention provides a method of controlling operation of a wind turbine having a tower. The method includes determining an overall control output including lateral oscillation control for dampening lateral oscillation of the tower, and using the overall control output to control wind turbine operation. The method further includes receiving lateral oscillation sensor data indicative of a level of lateral oscillation of the tower, determining a rated lateral oscillation control output in dependence on the received lateral oscillation data, and receiving an indication of yaw error of the wind turbine. A lateral oscillation control output included in the overall control output is determined to be de-rated from the rated lateral oscillation control output when the indicated yaw error is above a predetermined lower threshold level.

A wind turbine comprising a tower (2) with a tower wall and having at least one nacelle (3) mounted thereon, and a yaw system (1) interconnecting the tower (2) and at least one nacelle (3) is disclosed. The yaw system (1) comprises a yaw claw (4) comprising an upper radially extending part (5), a lower radially extending part (6) and an axially extending part (7) interconnecting the upper radially extending part (5) and the lower radially extending part (6), thereby defining a space. A sliding bearing connection with at least two axial sliding surfaces (9, 10) and at least one radial sliding surface (11) is arranged between the yaw claw (4) and a flange (8) arranged in the space defined by the yaw claw (4). At least one yaw drive (13) comprising a toothed gear (14) is arranged in meshing connection with a toothed yaw ring (12). The axially extending part (7) of the yaw claw (4) and the meshing connection between the toothed gear (14) and the toothed yaw ring (12) are arranged at the same side of the tower wall.

The present disclosure relates to methods for determining reliability of an azimuth measurement system in a wind turbine. The methods comprise measuring loads with load sensors during operation and determining in-plane moments with rotor rotational speed frequency of one or more blades based on the measured loads. The methods further comprise measuring an azimuthal position of a wind turbine rotor. The method also comprises determining that the azimuth measurement system has reduced reliability if an angular phase of the in-plane moments deviates from the measured azimuthal position by more than a first threshold value. The present disclosure also relates to wind turbine systems incorporating azimuth measurements and methods for on-line determination of correct functioning of azimuth sensors.

A method for determining a yaw position offset of a wind turbine (1) is provided. A neighbouring wind turbine (2) of the wind farm is identified, the neighbouring wind turbine (2) being arranged in the vicinity of the wind turbine (1). Produced power data and/or wind speed data from the wind turbine (1) and from the neighbouring wind turbine (2), is obtained during a period of time, and a yaw position offset of the wind turbine (1) is derived, based on the obtained produced power data and/or wind speed data, and based on the geographical positions of the wind turbine (1) and the neighbouring wind turbine (2). A local maximum and a local minimum being separated by an angular difference in yaw position being substantially equal to 180°.

The invention relates to a method for monitoring yawing fault events of a yaw system of a wind turbine. The yaw system comprises one or more actuators for driving the yaw system and a holding system to resist yaw rotation. The yaw system is arranged to provide yaw rotation in response to a yaw control signal. According to the method, the monitored yaw angle is compared with the yaw control signal, and based on the comparison, a correlation between a monitored change in the yaw angle and the yaw control signal is determined. A yawing fault event is determined dependent on the determined correlation.

A method and associated system are provided for determining a yaw heading (θ.sub.heading) of a wind turbine, the wind turbine having a tower and a nacelle that includes a machine head and rotor at a top thereof. The method includes configuring a single rover receiver of a global navigation satellite system (GNSS) at a fixed position relative to the nacelle. A GNSS geographic location of a tower top pivot point (TPP) of the wind turbine is determined, as well as an angular offset of the rover receiver (β.sub.rover) relative to a centerline axis of the nacelle. Based on the GNSS geo-location of the TPP and a GNSS geo-location of the rover receiver, an angular vector () relative to North of a line between the TPP and the rover receiver is determined. The yaw heading (θ.sub.heading) is computed from a difference between the angle () and the angular offset (β.sub.rover) of the rover receiver.

The invention relates to a method for identifying an asymmetrical extreme load which is caused by a gust of wind and acts on a wind power installation, wherein the wind power installation has a rotor having at least three rotor blades; the rotor blades are adjustable in terms of the blade angle thereof; and the rotor by way of the rotor blades thereof sweeps a rotor field; and the method comprises continuous detecting of a blade load for each rotor blade; ascertaining for at least one sector of the rotor field at least one temporal sector load profile from blade loads detected of different rotor blades with the same azimuth position, said sector load profile describing a temporal profile of a load on the rotor blades in the sector and containing a profile extrapolated for a future temporal period, wherein the blade loads are detected or taken into account at successive detection time points which are spaced apart by a partial period in which the rotor rotates further by one rotor blade, so that successive blade loads are detected or taken into account for the respective sector; and checking in terms of expecting an extreme load as a function of the at least one sector load profile.

A pitch control method and system of a symmetrical-airfoil vertical axis wind turbine collects data by an anemometer, an anemoscope and an angle sensor, outputs an optimum pitch angle based on a control law of a pitch angle and controls the pitch angle to be the optimum pitch angle through a pitch control actuator. In addition to input variables of the control law such as a wind velocity v.sub.in and a blade azimuth angle Ψ, constants such as a rotation radius R, a rotation velocity Ω of the blade and aerodynamic coefficients c.sub.1, c.sub.2 and c.sub.3 are also related. A Reynolds number has little influence on three aerodynamic coefficients c.sub.1, c.sub.2 and c.sub.3. The pitch actuator controls the adjustment rods to realize the automatic pitch control of the blades. An expression of the control law of the pitch is concise, the calculation time is short, and a response speed is fast.

Systems and methods of autonomous farm-level control and optimization of wind turbines are provided. Exemplary embodiments comprise a site controller running on a site server. The site controller collects and analyzes yaw control data of a plurality of wind turbines and wind direction data relating to the plurality of wind turbines. The site server determines collective wind direction across an area occupied by the plurality of wind turbines and sends yaw control signals including desired nacelle yaw position instructions to the plurality of wind turbines. The site controller performs wake modeling analysis and determines desired nacelle positions of one or more of the plurality of wind turbines. The desired nacelle yaw position instructions systematically correct static yaw misalignment for all of the plurality of wind turbines. Embodiments of the disclosure provide means to perform whole site or partial site level controls of the yaw controllers of a utility scale wind turbine farm. The overall effect of the coordinated yaw control of wind turbines across the whole or partial site is intended to keep the wake loss of the wind turbines from the upstream wind turbines to the minimum and to maximize the production of turbines that are not waking other turbines.