Damping of a wind turbine tower oscillation

A computer program product having instructions which, when executed cause a computing device or a computing system or a control system for a wind turbine to perform an operation for damping an oscillation of a tower of the wind turbine, wherein the operation further comprises:

• preparing a precursor signal for each rotor blade of the wind turbine, where each precursor signal comprises:
• a first periodic component with a first amplitude which is larger than zero, and where the first frequency of the first periodic component corresponds to the frequency difference between a tower frequency and a rotor frequency,
• and
• a second periodic component with a second amplitude which is larger than zero, and where a second frequency of the second periodic component corresponds to a frequency sum of the tower frequency and the rotor frequency,
• based on the precursor signal, preparing a tower damping pitch control signal for each rotor blade;
• wherein the second amplitude of the second periodic component has been partially or fully reduced relative to the first amplitude of the first periodic component;
• and
• damping the oscillation of the tower by pitching each rotor blade individually according to the tower damping pitch control signals.

A wind turbine, comprising:

• a tower;
• a nacelle disposed on the tower;
• a generator disposed in the nacelle;
• a rotor coupled to the generator;
• a plurality of rotor blades coupled to the rotor;
• a control system configured to perform an operation, comprising:
• preparing a precursor signal for each rotor blade, where each precursor signal comprises:
• a first periodic component with a first amplitude which is larger than zero, and where the first frequency of the first periodic component corresponds to the frequency difference between a tower frequency and a rotor frequency,
• and
• a second periodic component with a second amplitude which is larger than zero, and where a second frequency of the second periodic component corresponds to a frequency sum of the tower frequency and the rotor frequency,
• based on the precursor signal, preparing a tower damping pitch control signal for each rotor blade;
• wherein the second amplitude of the second periodic component has been at least partially reduced relative to the first amplitude of the first periodic component;
• and
• damping the oscillation of the tower by pitching each rotor blade individually according to the tower damping pitch control signals.