Abstract: Methods of controlling a variable speed wind turbine generator connected to a power grid. The method may include measuring the frequency, f, of the power grid, controlling the speed of the generator for optimizing the power delivered to the power grid, and setting limits for the generator speed. The setting of the limits for the generator speed is performed in dependency of the measured frequency of the power grid. This provides a dynamical set of limits providing improved possibilities of optimizing the power production.

Abstract: The present invention relates to a pitch control system for operating the blade pitch of the rotor blades of a wind turbine generator. A method is disclosed wherein a command signal or pitch demand is applied to the blade pitch system of the rotor blades and the resulting response signal or pitch response is received. The received pitch response is compared to a reference and a signal indicative of a pitch system fault may be generated if a difference between the response signal and the reference is detected as being larger than a preset criterion. The deviating behaviour of a blade pitch system can thereby be detected which enables a testing or monitoring of the condition of the pitch system of the rotor blades of a wind turbine generator.

Abstract: A method of controlling a wind turbine, where a control signal for a controllable parameter of the wind turbine is determined, and the rotor power coefficient, the torque coefficient, and/or a thrust coefficient of the wind turbine are estimated at time intervals. From this is determined a variation parameter reflecting the variation of the estimated rotor power, torque or thrust coefficient over time. The wind turbine is then controlled according to the control signal only if the variation parameter is below an alert threshold, and otherwise according to a modified control strategy. The control signal may have a power or torque reference signal for controlling the rotational speed of the turbine or a blade pitch reference signal. The modified control method may for instance entail stopping or de-rating the wind turbine. A control system configured to perform the above control method, and a wind turbine comprising such system are also disclosed.

Abstract: in a method of controlling a variable speed wind turbine, said wind turbine comprising a double-fed asynchronous generator having rotor windings and stator windings and means for controlling the wind turbine speed, the method comprises the following steps:—measuring or calculating, based on measured parameters, the active electrical power (Pr) in the rotor windings, comparing the active electrical power (Pr) in the rotor windings with a preset limit (PrLimit), when the active electrical power (Pr) in the rotor windings exceeds the preset limit (PrLimit), controlling the wind turbine speed to minimize the difference between the active electrical power (Pr) in the rotor windings and a preset reference (PrRef). The rotor power (Pr) is kept at a reduced level, thus avoiding overload of wind turbine generator components.

Abstract: A method of controlling a wind turbine, where a control signal for a controllable parameter of the wind turbine is determined, and the rotor power coefficient, the torque coefficient, and/or a thrust coefficient of the wind turbine are estimated at time intervals. From this is determined a variation parameter reflecting the variation of the estimated rotor power, torque or thrust coefficient over time. The wind turbine is then controlled according to the control signal only if the variation parameter is below an alert threshold, and otherwise according to a modified control strategy. The control signal may have a power or torque reference signal for controlling the rotational speed of the turbine or a blade pitch reference signal. The modified control method may for instance entail stopping or de-rating the wind turbine. A control system configured to perform the above control method, and a wind turbine comprising such system are also disclosed.

Abstract: The invention provides a wind turbine comprising a wind-driven rotor for converting wind energy to a mechanical driving force, a power converter for converting the driving force to exploitable power and a transmission system for rotatably transmitting the driving force to the power converter. The transmission system comprises at least one rotatable driving element and a torsional dampening device having a rotatable inertia element which is drivable by the at least one rotatable driving element. The inertia element is connected in such a way to the at least one rotatable driving element that the inertia element dampens torsional vibrations in the rotatable driving element during operation of the wind turbine.