A method for operating a wind farm is provided. The wind farm includes at least two groups of wind turbines, each of the at least two groups of wind turbines includes at least one wind turbine of the wind farm, each of the wind turbines of the wind farm belonging to one of the at least two groups of wind turbines. The method includes determining a power setpoint for the wind farm, determining a group curtailment setpoint for each of at least two groups of wind turbines, determining a power production value of each of the at least two groups of wind turbines, determining for each of the at least two groups of wind turbines a power reference value using the respective group curtailment setpoint and the respective power production value, determine for each of the at least two groups of wind turbines a group power setpoint which is proportional to the respective power reference values, and operating the at least two groups of wind turbines in accordance with the respective group power setpoint. Furthermore, a wind farm is provided.

A method for operating a wind farm is provided. The wind farm includes at least two groups of wind turbines, each of the at least two groups of wind turbines includes at least one wind turbine of the wind farm, each of the wind turbines of the wind farm belonging to one of the at least two groups of wind turbines. The method includes determining a power setpoint for the wind farm, determining a group curtailment setpoint for each of at least two groups of wind turbines, determining a power production value of each of the at least two groups of wind turbines, determining for each of the at least two groups of wind turbines a power reference value using the respective group curtailment setpoint and the respective power production value, determine for each of the at least two groups of wind turbines a group power setpoint which is proportional to the respective power reference values, and operating the at least two groups of wind turbines in accordance with the respective group power setpoint. Furthermore, a wind farm is provided.

A method for calibrating a wind direction measurement for a wind turbine is provided. The method including: measuring plural samples of a relative wind direction representing a difference angle between a real wind direction and an orientation of a measurement equipment, in particular a direction orthogonal to a rotor blade plane, to obtain plural measured relative wind directions; deriving a measured relative wind direction change based on the measured relative wind directions; measuring plural samples of a performance parameter indicating a performance of the wind turbine; deriving a performance change based on the plural samples of the performance parameter; determining a correlation value between the measured relative wind direction change and the performance change; measuring further plural samples of the relative wind direction; and correcting the further measured relative wind directions based on the correlation value, to obtain corrected further measured relative wind directions.

Provided is a method for performing a wind direction measurement for a wind turbine, the method including: measuring plural sample pairs, each pair including a measured relative wind direction and an associated performance quantity, the measured relative wind direction representing a measurement result of measuring a difference angle between a real wind direction and an orientation of a measurement equipment, in particular a direction orthogonal to a rotor blade plane, the performance quantity indicating a performance of the wind turbine; evaluating a degree of asymmetry of the performance quantity with respect to a measured relative wind direction equal to zero; measuring a further relative wind direction; and correcting the further measured relative wind direction based on the degree of asymmetry.

A wind turbine is provided. The wind turbine includes a transformer having a low-voltage side and a high-voltage side. The transformer is configured to step up a voltage of the low-voltage side of the transformer to a voltage of an external grid. The wind turbine further includes an electrical power generating unit which is connected to the low-voltage side of the transformer and configured to feed an ac-power to the low-voltage side of the transformer. A charging device of the wind turbine is connected to the low-voltage side of the transformer and configured to charge the low-voltage side of the transformer when the generator does not feed ac-power to the low-voltage side of the transformer.

A wind turbine is provided. The wind turbine includes a transformer having a low-voltage side and a high-voltage side. The transformer is configured to step up a voltage of the low-voltage side of the transformer to a voltage of an external grid. The wind turbine further includes an electrical power generating unit which is connected to the low-voltage side of the transformer and configured to feed an ac-power to the low-voltage side of the transformer. A charging device of the wind turbine is connected to the low-voltage side of the transformer and configured to charge the low-voltage side of the transformer when the generator does not feed ac-power to the low-voltage side of the transformer.

The invention relates to techniques for verifying a nacelle yaw position sensor installed on a wind turbine and for taking restorative action to control the nacelle yaw position. The invention relates to a method performing the comprising determining a first absolute wind direction signal associated with the first wind turbine; determining a second absolute wind signal direction signal associated with the plurality of other wind turbines; comparing the two wind direction signals; and issuing a nacelle yaw position sensor fault signal if the first signal is beyond a predetermined error range of the second signal. A benefit of the invention is that it enables the detection of an inaccurate nacelle yaw sensor without direct measurement or inspection.

A method of controlling a dynamic physical system comprising a plurality of variable quantities. A model of the system comprising a plurality of variables representing the variable quantities, and a plurality of respective rate equations that describe the rate of change of the variables, is obtained. A control term in at least one rate equation from the plurality of rate equations is identified. A rate control function is derived from, for at least one of the variables in the rate equation, the proportion of the variable to the growth rate of the rate equation, and the rate control function is applied to the control term to provide a stabilized control term. The dynamic physical system is then controlled by modifying at least one of the quantities represented by the variables in the control term, so that the control term derived from the modified quantities is substantially the same as the stabilized control term.

A method of controlling a dynamic physical system comprising a plurality of variable quantities. A model of the system comprising a plurality of variables representing the variable quantities, and a plurality of respective rate equations that describe the rate of change of the variables, is obtained. A control term in at least one rate equation from the plurality of rate equations is identified. A rate control function is derived from, for at least one of the variables in the rate equation, the proportion of the variable to the growth rate of the rate equation, and the rate control function is applied to the control term to provide a stabilized control term. The dynamic physical system is then controlled by modifying at least one of the quantities represented by the variables in the control term, so that the control term derived from the modified quantities is substantially the same as the stabilized control term.

A static testing and calibrating method for PID link of control system of wind turbine includes following steps. A PID control link of the PID link of the control system of wind turbine is tested. A PID regulator response characteristics is tested. The PID link of control system is calibrated by applying test results of the PID control link and the PID regulation response characteristics.