Provided is a safety stop valve arrangement of a hydraulic blade pitch system of a wind turbine, including an accumulator arrangement connected over a hydraulic line to a piston of the hydraulic blade pitch system; a redundant set of safety valves arranged between the accumulator arrangement and the piston; a small-orifice restriction nozzle arranged to determine a first rate of hydraulic fluid flow in response to a safety stop input; at least one speed-select valves arranged; and at least one large-orifice restriction nozzle arranged to determine a second rale of hydraulic fluid flow in response to a positive rotor acceleration input, wherein the second rate of fluid flow is faster than the first rate of fluid flow. A safety stop assembly of a wind turbine with hydraulic blade pitch systems and a method of performing a safety stop sequence is also provided.

A system and method are provided for controlling a wind farm during low wind speeds. Accordingly, the farm controller designates at least one of the plurality of wind turbines of the wind farm as a designated turbine. The designated turbine is operating in a full auxiliary mode when the speed of the wind acting on the wind farm is below a wind speed threshold. The remaining wind turbines are operated in a reduced auxiliary mode. The reduced auxiliary mode includes the disabling of at least one of pitching and yawing of the remaining wind turbines. When a power output for the designated wind turbine exceeds a power threshold, the farm controller directs at least one group of the remaining wind turbines to transition from the reduced auxiliary mode to the full auxiliary mode. During certain grid conditions, the transition between auxiliary modes may be delayed.

A wind turbine has a Lidar device to sense wind conditions upstream of the wind turbine. Signals from the wind turbine are processed to detect an extreme change in wind direction. The detection is performed by differentiating the rate of change of wind direction and filtering for a period of time. On detection of extreme change the system controller takes the necessary evasive action which may include shutting down the turbine, commencing an immediate yawing action, and de-rating the turbine until the yawing action is complete.

The invention relates to a method for controlling a yaw offset of a plurality of wind turbines. The method uses a decision function which generates an activation parameter for determining if the yaw offset control of a specific wind turbine should be enabled or disabled. The decision function depends on two or more variables comprising a wind direction variable indicative of the wind direction of the specific wind turbine, and a wind variation variable defining at least a wind variation range where yaw offset control is disabled or enabled. Based on the decision function it is determined if a yaw offset should be added to the current yaw setting of the specific wind turbine.

Provided are a control method and apparatus for load reduction of a wind turbine. The control method for load reduction includes: determining a representative blade root load value of a wind turbine; determining an additional pitch rate value based on the representative blade root load value; determining a pitch rate control value based on a given pitch rate value and the additional pitch rate value: and applying the pitch rate control value to each blade of the wind turbine, to control each blade of the wind turbine to perform a pitch action.

A wind turbine has a Lidar device to sense wind conditions upstream of the wind turbine. Wind speed signals from the wind turbine are processed to detect an extreme operating gust. The detection is performed by differentiating the axial wind velocity and filtering for a period of time. On detection of extreme operating gust the system controller takes necessary evasive action which may include shutting down the turbine or varying the blade pitch angle.

The invention relates to a method for limiting structural loads in a wind turbine in situations where the power produced by the wind turbine is increased or decreased. The limitation of structural loads is achieved by restricting the power ramp rate, i.e. the rate of change of increases or decreases in produced power. The restriction is only invoked if a maximum change of the produced power or the corresponding internal power reference within a time window exceeds a given threshold.

A system and method are provided for controlling a wind turbine. Accordingly, a controller of the wind turbine detects a loss of traction of the slip coupling between a generator and a rotor of the drivetrain of the wind turbine. In response to detecting the loss of traction, the controller overrides a generator torque setpoint to alter a rotational speed of the generator. In response to the altered rotational speed of the generator, the traction of the slip coupling is increased. Increasing the traction of the slip coupling facilitates an application of generator torque to the drivetrain of the wind turbine.

The present invention relates to a system and method for controlling an output evaporation rate of a wind power plant. The system includes a wind power plant control unit configured to measure an output value of a wind power plant before a predetermined time from an output control time of the wind power plant, calculate a maximum output value of the wind power plant on the basis of the measured output value of the wind power plant, and distributing individual maximum output values of the wind power plant to individual wind power generators in the wind power plant and a wind power generator control unit configured to control outputs of the individual wind power generators according to the individual maximum output values when the individual maximum output values are distributed to the individual wind power generators.

A wind turbine includes a rotor, a plurality of rotor blades coupled to the rotor, and a blade pitch control system coupled to each rotor blade. A computer-implemented method for controlling the wind turbine includes determining at least one pitch position for a first blade. The method also includes determining whether there is a malfunction of the blade pitch control system associated with the first blade. The method further includes predicting a rotor imbalance using a model of at least a portion of the wind turbine. The method also includes comparing the predicted rotor imbalance with a predetermined threshold value. The method further includes one of regulating the pitch position for the second blade such that the predicted rotor imbalance is restored to a value below the predetermined threshold and regulating a pitch position for a second blade such that the predicted rotor imbalance does not exceed the predetermined threshold.