Abstract: A method for controlling a wind turbine using an estimated wind speed is provided. The wind turbine has a rotor rotatable with a variable rotor speed and having rotor blades with adjustable pitch angles and a generator adapted to control a generator torque or a generator output power. The method comprises measuring the rotor speed, determining a common pitch angle representative of at least one or all pitch angles of the rotor blades, determining the generator torque or an output power of the generator and estimating the wind speed by means of an observer. The observer uses a model of the wind turbine as an observer model, uses as input variables, the measured rotor speed, the determined common pitch angle and the determined generator torque or the determined output power, and incorporates expected variations of the wind as at least one stochastic variable.

Abstract: A method for controlling a wind turbine, the wind turbine having a generator with controllable generator torque and an aerodynamic rotor with rotor blades with adjustable pitch angle, the aerodynamic rotor driving the generator with variable rotor speed depending on a wind speed, comprising the steps operating the wind turbine in a subrated mode when the wind speed is below a predetermined rated wind speed, operating the wind turbine in a rated mode when the wind speed is at or above the predetermined rated wind speed, estimating the wind speed and operating the wind turbine in subrated mode or in rated mode in dependence on the estimated wind speed.