System and method for determining an estimated position of a wind turbine rotor shaft

1. A method for determining an estimated rotor shaft position of a rotor shaft of a wind turbine, the method comprising:

generating, with a rotor shaft position sensor, a measured rotor shaft position signal associated with a measured rotor shaft position of the rotor shaft;

generating, with a plurality of accelerometers positioned in an axisymmetric arrangement, a plurality of rotor hub acceleration signals associated with a plurality of rotor hub accelerations of a rotor hub coupled to the rotor shaft;

determining, with a controller, a phase adjustment based on one of the plurality of rotor hub acceleration signals or a predetermined correction value; and

adjusting, with the controller, the measured rotor shaft position by the phase adjustment to determine the estimated rotor shaft position of the rotor shaft of the wind turbine.

2. The method of claim 1 , further comprising: determining, with the controller, the phase adjustment based on the plurality of rotor hub acceleration signals.

3. The method of claim 1 , further comprising:

determining, with the controller, the phase adjustment based on the predetermined correction value when the controller does not receive the plurality of rotor hub acceleration signals from the plurality of accelerometers.

4. The method of claim 1 , further comprising:

receiving, with the controller, the measured rotor shaft position signal from the rotor shaft position sensor;

receiving, with the controller, the plurality of rotor hub acceleration signals from the plurality of accelerometers; and

calculating, with the controller, a rotating frame of reference rotor shaft acceleration of the rotor shaft based on the plurality of rotor hub acceleration signals.

5. The method of claim 4 , further comprising:

calculating, with the controller, an estimated fixed frame of reference rotor shaft acceleration of the rotor shaft based on the rotating frame of reference rotor shaft acceleration.

6. The method of claim 5 , further comprising:

filtering the estimated fixed frame of reference rotor shaft acceleration with a filter.

7. The method of claim 5 , further comprising:

determining, with the controller, the phase adjustment based on the estimated fixed frame of reference rotor shaft acceleration.

8. The method of claim 1 , further comprising:

receiving, with a phase locked loop of the controller, the estimated rotor shaft position;

determining, with the phase locked loop of the controller, an updated estimated rotor shaft position of the rotor shaft based on the plurality of rotor hub acceleration signals.

9. The method of claim 1 , further comprising:

calculating, with the controller, a rotating frame of reference rotor shaft acceleration of the rotor shaft based on the plurality of rotor hub acceleration signals;

calculating, with the controller, an estimated fixed frame of reference rotor shaft acceleration of the rotor shaft based on the rotating frame of reference rotor shaft acceleration; and

determining, with a phase locked loop of the controller, an updated estimated rotor shaft position of the rotor shaft based on the estimated fixed frame of reference rotor shaft acceleration.

10. A system for determining an estimated rotor shaft position of a rotor shaft of a wind turbine, the system comprising:

a rotor hub coupled to the rotor shaft and a plurality of rotor blades;

a rotor shaft position sensor operatively coupled to the rotor shaft for detecting a measured rotor shaft position of the rotor shaft and generating a measured rotor shaft position signal associated with the measured rotor shaft position;

a plurality of accelerometers operatively coupled to the rotor hub and positioned in an axisymmetric arrangement about the rotor shaft, the plurality of accelerometers measuring a plurality of rotor hub accelerations of the plurality of rotor blades and generating a plurality of rotor hub acceleration signals associated with the plurality of rotor hub accelerations; and

a controller communicatively coupled to the rotor shaft position sensor and the plurality of accelerometers, the controller configured to:

determine a phase adjustment based on one of the plurality of rotor hub acceleration signals or a predetermined correction value; and

adjust the measured rotor shaft position by the phase adjustment to determine the estimated rotor shaft position of the rotor shaft of the wind turbine.

11. The system of claim 10 , wherein the controller is configured to determine the phase adjustment based on the plurality of rotor hub acceleration signals.

12. The system of claim 10 , wherein the controller is configured to determine the phase adjustment based on the predetermined correction value when the controller does not receive the plurality of rotor hub acceleration signals from the plurality of accelerometers.

13. The system of claim 10 , wherein the controller is configured to:

receive the measured rotor shaft position signal from the rotor shaft position sensor;

receive the plurality of rotor hub acceleration signals from plurality of accelerometers; and

calculate a rotating frame of reference rotor shaft acceleration of the rotor shaft based on the plurality of rotor hub acceleration signals.

14. The system of claim 13 , wherein the controller is configured to calculate an estimated fixed frame of reference rotor shaft acceleration of the rotor shaft based on the rotating frame of reference rotor shaft acceleration.

15. The system of claim 14 , further comprising:

a filter for filtering the estimated fixed frame of reference rotor shaft acceleration.

16. The system of claim 14 , wherein the controller is configured to determine the phase adjustment based on the estimated fixed frame of reference rotor shaft acceleration.

17. The system of claim 10 , wherein the controller comprises a phase locked loop configured to:

receive the estimated rotor shaft position when the controller does not receive the measured rotor shaft position signal from the rotor shaft position sensor; and

determine an updated estimated rotor shaft position of the rotor shaft based on the plurality of rotor hub acceleration signals.

18. The system of claim 17 , wherein the controller is configured to calculate a rotating frame of reference rotor shaft acceleration of the rotor shaft based on the plurality of rotor hub acceleration signals and to calculate an estimated fixed frame of reference rotor shaft acceleration of the rotor shaft based on the rotating frame of reference rotor shaft acceleration, and wherein the phase locked loop of the controller is configured to determine the updated estimated rotor shaft position of the rotor shaft based on the estimated fixed frame of reference rotor shaft acceleration.

19. A wind turbine, comprising:

a tower;

a nacelle mounted on the tower;

a rotor shaft at least partially positioned in the nacelle;

a rotor hub coupled to the rotor shaft;

a plurality of rotor blades coupled to the rotor hub;

a rotor shaft position sensor operatively coupled to the rotor shaft for detecting a measured rotor shaft position of the rotor shaft and generating a measured rotor shaft position signal associated with the measured rotor shaft position;

a plurality of accelerometers operatively coupled to the rotor hub and positioned in an axisymmetric arrangement about the rotor shaft, the plurality of accelerometers measuring a plurality of rotor hub accelerations of the rotor hub and generating a plurality of rotor hub acceleration signals associated with the plurality of rotor hub accelerations; and

a controller communicatively coupled to the rotor shaft position sensor and the plurality of accelerometers, the controller configured to determine an estimated rotor shaft position of the rotor shaft based on the measured rotor shaft position signal and the plurality of rotor hub acceleration signals wherein the controller is configured to:

determine a phase adjustment based on one of the plurality of rotor hub acceleration signals or a predetermined correction value; and

adjust the measured rotor shaft position by the phase adjustment to determine the estimated rotor shaft position of the rotor shaft.