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.

A method for protecting a wind turbine from an extreme change in wind direction includes receiving a wind direction and/or a wind speed at the wind turbine. When a change in the wind direction or the wind speed exceeds a predetermined threshold, the method includes determining a margin to stall and/or zero lift of the at least one rotor blade of the wind turbine as a function of an angle of attack or change in the angle of attack at a blade span location of at least one rotor blade of the wind turbine. The method also includes implementing a corrective action for the wind turbine (without shutting down the wind turbine) when the margin to stall and/or zero lift exceeds a predetermined value so as to avoid stall and/or negative lift on the at least one rotor blade during operation of the wind turbine.

A method for adjusting a power parameter of a wind turbine is disclosed. The method includes determining a load parameter indicative of a mechanical load of the wind turbine; estimating a turbulence of a wind speed based on the determined load parameter; and adjusting the power parameter relating to a power of the wind turbine based on the estimated turbulence. A system for adjusting a power parameter of a wind turbine is also described.

Method of operating a wind turbine in response to a wind speed, the wind turbine having at least a rotor with a plurality of blades and a generator comprising a generator rotor and a generator stator, the method comprising, at wind speeds above a first wind speed, increasing the pitch angle of the blades and reducing the rotor speed with increasing wind speed, said first wind speed being superior to the nominal wind speed; wherein at a second wind speed, the speed of the generator rotor is equal to the synchronous generator rotor speed, said second wind speed being superior to said first wind speed; and wherein at wind speeds superior to said second wind speed, the speed of the generator rotor is lower than the synchronous generator rotor speed.

A pitch control method and system of a symmetrical-airfoil vertical axis wind turbine is provided, which 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.

A method for operating a wind turbine is provided. The wind turbine has a tower with external tower loads acting thereon and has an aerodynamic rotor with rotor blades having adjustable pitch angles, which rotor generates rotor thrust. The method comprises the following steps: determining a speed of a tower head of the tower and/or of a nacelle of the wind turbine, determining an absolute wind speed in the region of the wind turbine, determining a pure wind power on the rotor on the basis of the absolute wind speed, determining an apparent wind power on the rotor on the basis of the speed of the tower head and/or of the nacelle, determining an aerodynamic tower vibration power on the basis of a difference between the apparent wind power and the pure wind power, and performing feedback control of the wind turbine using the aerodynamic tower vibration power.

A system comprising a blade pitch system having a set of locking holes. A pitch drive assembly is coupled to the blade pitch system and configured to rotate clockwise or counterclockwise within a range of angular degrees to adjust a blade pitch angle. The system includes a pitch lock pin-and-hole system including an interface plate and at least one blade pitch lock assembly coupled to the interface plate. Each lock assembly includes a locking pin having a pin center axis parallel with a center axis of a locking hole to engage a respective one locking hole of the set to lock the blade pitch angle.

A method for operating a wind turbine is provided. The wind turbine has a tower with external tower loads acting thereon and has an aerodynamic rotor with rotor blades having adjustable pitch angles, which rotor generates rotor thrust. The method comprises the following steps: determining a speed of a tower head of the tower and/or of a nacelle of the wind turbine, determining an absolute wind speed in the region of the wind turbine, determining a pure wind power on the rotor on the basis of the absolute wind speed, determining an apparent wind power on the rotor on the basis of the speed of the tower head and/or of the nacelle, determining an aerodynamic tower vibration power on the basis of a difference between the apparent wind power and the pure wind power, and performing feedback control of the wind turbine using the aerodynamic tower vibration power.

A method for controlling a wind turbine and an associated wind turbine. The wind turbine is operated according to an operating point, wherein the operating point is determined at least by a pitch angle and a tip speed ratio, wherein one of the operating points corresponds to a maximum power coefficient, wherein, in a partial load range, the wind turbine is operated at an operating point which differs from the operating point with the maximum power coefficient. The distance of the operating point from the operating point with the maximum power coefficient is set in accordance with a measured turbulence measure.

A wind turbine and method are provided for defining a plurality of thrust limits for the wind turbine located at a site and having a rotor with rotor blades, wherein the thrust limits define values of aerodynamic thrust on the rotor not to be exceeded in operation. The method includes providing a wind speed distribution representative for the site and defining one or more isolines of constant turbulence probability representing a turbulence parameter as a function of wind speed. The isolines correspond to quantile levels of turbulence of the wind speed distribution and the turbulence parameter is indicative of wind speed variation. The turbulence parameter is determined by continuously measuring wind speed upstream of the rotor with an active sensing system and calculating the wind speed variations from the measured wind speed. Turbulence ranges are defined with respect to the isolines and thrust limits are defined for the turbulence ranges.