System and method for use of an automatically tunable spring mass damper to reduce vibrations in wind turbine blades

A wind turbine configured for reducing vibrations and loads in rotor blades during a non-operational mode of the wind turbine, comprising:

• a plurality of rotor blades on a rotor hub;
• in the non-operational mode of the wind turbine with the rotor hub in a locked or idling condition, the wind turbine further comprising a tunable spring mass damper attached at a fixed location on one or more of the rotor blades, the spring mass damper comprising a mass component that is movable along a stroke path;
• one or more sensors configured with the spring mass damper to sense movement of the mass component along the stroke path, wherein the movement is generated by vibrations or oscillations induced in the rotor blades during the locked or idling condition of the rotor hub;
• the spring mass damper comprising an electric machine operable as a motor or a generator;
• and
• a controller configured with the spring mass damper and configured to perform one or both of the following:
• (a) based on the sensed movement of the mass component, automatically tune the spring mass damper to an amplitude of the vibrations by operating the electric machine as a generator in a virtual damper mode;
• or (b) automatically tune the spring mass damper to the frequency of the vibrations by operating the electrical machine as a motor-generator in a virtual spring mode.

A system for reducing vibrations and loads in rotor blades of a wind turbine during a non-operational mode of the wind turbine wherein a rotor hub of the wind turbine is in a locked or idling condition, the system comprising:

• a tunable spring mass damper configured for attachment at a fixed location on one or more of the rotor blades, the spring mass damper comprising a mass component that is movable along a stroke path;
• one or more sensors configured with the spring mass damper to sense movement of the mass component along the stroke path, wherein the movement is generated by vibrations or oscillations induced in the rotor blades during the locked or idling condition of the rotor hub;
• the spring mass damper comprising an electric machine operable as a motor or a generator;
• and
• a controller configured with the spring mass damper and configured to perform one or both of the following:
• (a) based on the sensed movement of the mass component, automatically tune the spring mass damper to an amplitude of the vibrations by operating the electric machine as a generator in a virtual damper mode;
• or (b) automatically tune the spring mass damper to the frequency of the vibrations by operating the electrical machine as a motor-generator in a virtual spring mode.