Method for operating a wind turbine, controller, wind turbine and wind farm

A method for operating a wind turbine, comprising:

• determining a speed of a tower head of a tower and/or a nacelle of the wind turbine, wherein external tower loads act on the tower, the wind turbine has an aerodynamic rotor including a plurality of rotor blades that have adjustable pitch angles, and the rotor is configured to generate rotor thrust;
• determining an absolute wind speed in a region of the wind turbine,
• determining a pure wind moment on the rotor based on the absolute wind speed;
• determining an apparent wind moment on the rotor based on the speed of the tower head;
• determining an aerodynamic tower vibration moment based on a difference between the apparent wind moment and the pure wind moment;
• and
• performing feedback control of the wind turbine using the aerodynamic tower vibration moment.

A feedback controller for a wind turbine, comprising:

• an input configured to receive an input signal which includes a rotational speed change, a rotational speed acceleration, a function of the rotational speed change and/or a function of the rotational speed acceleration, wherein the wind turbine has an aerodynamic rotor including at least one rotor blade, wherein the feedback controller is configured to:
• determine a speed of a tower head of a tower and/or a nacelle of the wind turbine;
• determine an absolute wind speed in a region of the wind turbine;
• determine a pure wind power or a pure wind moment on the rotor based on the absolute wind speed;
• determine an apparent wind power or an apparent wind moment on the rotor based on the speed of the tower head and/or the nacelle;
• determine an aerodynamic tower vibration power based on a difference between the apparent wind power and the pure wind power or determining an aerodynamic tower vibration moment based on a difference between the apparent wind moment and the pure wind moment and
• perform feedback control of a rotational speed of the rotor using the aerodynamic tower vibration power or the aerodynamic tower vibration moment.