Abstract: A method of determining a degree of yaw error of a wind turbine is provided. The method includes obtaining wind pressure measurement values from in front of the rotor plane, which wind pressure measurement values exhibit a periodic nature related to a rotation of a spinner of the wind turbine, performing a signal processing step to process the wind pressure measurement values to determine a phase offset of the wind pressure measurement values relative to an angular reference, and deriving a yaw error angle from the phase offset. A method of establishing a relationship between a phase offset of wind pressure measurement values and a degree of yaw error of a wind turbine, a yaw error determination unit, and a wind turbine are also provided.

Abstract: A method for operating a wind turbine which includes a rotor hub supporting a rotor blade includes: a) detecting changes in the aerodynamic performance of the rotor blade; b) determining a first control rule; c) determining a first power output information indicating a first power output based on the first control rule; d) changing an operational parameter and choosing a second control rule such that the first control rule is replaced by the second control rule; e) determining a second power output information indicating a second power output based on the second control rule. c) comparing the first and second power output information. If the second power output exceeds the first power output, repeating a)-f) with the second control rule being used as the first control rule in b); otherwise repeating a)-f) a different second control rule is applied in d).

Abstract: A method of determining a degree of yaw error of a wind turbine is provided. The method includes obtaining wind pressure measurement values from in front of the rotor plane, which wind pressure measurement values exhibit a periodic nature related to a rotation of a spinner of the wind turbine, performing a signal processing step to process the wind pressure measurement values to determine a phase offset of the wind pressure measurement values relative to an angular reference, and deriving a yaw error angle from the phase offset. A method of establishing a relationship between a phase offset of wind pressure measurement values and a degree of yaw error of a wind turbine, a yaw error determination unit, and a wind turbine are also provided.

Abstract: A method for operating a wind turbine which includes a rotor hub supporting a rotor blade is disclosed. The method includes: a) detecting changes in the aerodynamic performance of the rotor blade; b) determining a first control rule; c) determining a first power output information indicating a first power output based on the first control rule; d) changing an operational parameter and choosing a second control rule such that the first control rule is replaced by the second control rule; e) determining a second power output information indicating a second power output based on the second control rule. c) comparing the first and second power output information. If the second power output exceeds the first power output, repeating a)-f) with the second control rule being used as the first control rule in b); otherwise repeating a)-f), whereby a different second control rule is applied in d).

Abstract: A method is provided for detecting a blade pitch angle unbalance of a rotor blade system of a wind turbine, the rotor blade system rotating around a rotor rotation axis. The method includes yawing the rotor rotation axis about a yawing axis transverse to the rotor rotation axis. The method also includes obtaining a load signal indicative of a load due to the yawing. The method further includes analyzing the load signal regarding a frequency component of the load signal, and detecting the blade pitch angle unbalance based on the analyzed load signal.

Abstract: A system for determining a vibrational frequency of a blade being attached to a structural component of a wind turbine is described. The blade is vibrating within a rotational plane of the rotor. A sensor sensitive to a movement along a sensor direction is placed at the structural component so the sensor direction and the direction of the longitudinal extension of the blade have a fixed angular relationship with respect to each other. The sensor is configured to provide a sensor output signal being indicative for the movement of the structural component along the sensor direction. A data processing unit is connected with the sensor and configured to determine the vibrational frequency of the blade based on the sensor output signal and on the fixed angular relationship. Corresponding wind turbine equipped with such a system, method for determining a vibrational frequency of a blade and computer program are provided.