Mitigating standstill vibrations of a wind turbine

An arrangement for mitigating a vibration of a wind turbine not receiving power from a utility grid, the arrangement comprising:

• an energy storage system of the wind turbine;
• a wind direction sensor;
• one or more vibration sensors;
• a yawing system;
• a processor,
• wherein the arrangement is adapted to supply power received from the energy storage system:
• to the wind direction sensor to detect a wind direction,
• to the yawing system to adjust an orientation of a rotor axis of a rotor shaft if the processor determines that a criterion is satisfied, wherein the criterion comprises at least a relative orientation of a rotor axis direction and the detected wind direction, and
• to detect a wind speed, wherein the criterion further comprises that the wind speed is in a wind speed range, depending on the wind direction relative to the rotor axis direction, wherein plural wind speed ranges are defined in association with different orientations of the wind direction relative to the rotor axis direction, wherein the criterion further comprises that at least one respective wind speed range associated with a respective orientation is present, wherein the at least one respective wind speed range is defined in that the wind speed is greater than a threshold depending on at least one of the different orientations.

A method of mitigating a vibration of a wind turbine not receiving power from a utility grid, the method comprising:

• receiving power from an energy storage system of the wind turbine;
• providing plural wind speed ranges defined in association with different orientations of the wind direction relative to a rotor axis direction of a rotor axis of a rotor shaft, wherein at least one of the wind speed ranges of the plural wind speed ranges is defined in that wind speed is greater than a threshold for at least one orientation of the different orientations of the wind direction relative to the rotor axis direction;
• detecting a wind direction and a wind speed;
• determining that a criterion is satisfied, wherein the criterion is based on the detected wind speed, wind direction, and a level of the vibration, wherein the criterion includes that at least one of the wind speed ranges of the plural wind speed ranges associated with the respective orientation is present;
• and
• adjusting an orientation of the rotor axis of the rotor shaft using the power received from the energy storage system of the wind turbine.