Relating to the determination of rotor imbalances in a wind turbine
A method and system for improving the balance of a rotor in a wind turbine, including; determining blade load data associated with a selected rotor blade pair; determining, based on the blade load data, pitch imbalance data associated with the selected rotor blade pair, wherein the pitch imbalance data associated with a rotor blade pair is based on measurements of at least blade loading, rotor speed and wind speed; and, determining and applying pitch control inputs to one or both of the selected rotor blade pair in order to reduce the severity of the rotor imbalance.
1. A method of improving balance of a rotor of a wind turbine, the method including;
selecting a rotor blade pair from a plurality of rotor blades coupled to the rotor;
receiving blade load data associated with each of the plurality of rotor blades, the blade load data comprising:
a blade loading of each of the plurality of rotor blades,
a speed of the rotor, and
a wind speed;
determining a pitch imbalance of the rotor associated with the selected rotor blade pair, the pitch imbalance based on a difference between blade load data associated with the selected rotor blade pair and blade load data associated with another rotor blade pair of the plurality of rotor blades; and
determining and applying pitch control inputs to one or both rotor blades of the selected rotor blade pair to reduce the pitch imbalance of the rotor.
2. The method of claim 1 , wherein determining the pitch imbalance associated with the selected rotor blade pair is provided by:
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.
3. The method of claim 1 , including determining the blade load data associated with two or more selected rotor blade pairs.
4. The method of claim 1 , wherein determining the blade load data includes acquiring a blade load data set associated with each blade of the selected rotor blade pair during conditions in which a rotor speed is substantially constant.
5. The method of claim 4 , wherein the rotor speed is maintained within +/−10% of a target speed.
6. The method of claim 4 , wherein the rotor speed is maintained within +/−5% of a target speed.
7. The method of claim 4 , wherein determining the blade load data includes acquiring a blade load data set associated with each blade of the selected rotor blade pair during conditions in which the wind speed is constant to within +/−25%.
8. The method of claim 4 , wherein determining the blade load data includes acquiring a blade load data set associated with each blade of the selected rotor blade pair during conditions in which the wind speed is constant to within +/−10%.
9. The method of claim 1 , further including, before the step of determining and applying pitch control inputs, checking that the pitch imbalance associated with the selected rotor blade pair exceeds a predetermined threshold.
10. A wind turbine system comprising a rotor having a plurality of rotor blades, each of the rotor blades being equipped with blade load sensing means and a blade pitch control means, the system further comprising a controller configured to:
select a rotor blade pair from the plurality of rotor blades;
receive blade load data associated with each of the plurality of rotor blades, the blade load data comprising:
a blade loading of each of the plurality of rotor blades,
a speed of the rotor, and
a wind speed;
determine a pitch imbalance of the rotor associated with the selected rotor blade pair, the pitch imbalance based on a difference between blade load data associated with the selected rotor blade pair and blade load data associated with another rotor blade pair of the plurality of rotor blades; and
determine and apply pitch control inputs to one or both rotor blades of the selected rotor blade pair to reduce the pitch imbalance of the rotor.