System and method for estimating high bandwidth tower deflection for wind turbines

1. A method comprising:

estimating tower loads of a wind turbine by:

receiving, via a controller, an estimate of slow variations in thrust of a tower of the wind turbine, wherein slow variations include variations in frequency lower than a tower natural frequency;

determining, via one or more sensors, tower accelerations of the tower of the wind turbine;

estimating, via the controller, the tower loads of the wind turbine as a function of the estimate of slow variations in thrust of the tower and the tower accelerations; and

initiating control actions for the wind turbine when the estimated tower loads are at a design limit, the control actions comprising at least one of controlling an operating mode of the wind turbine, starting up the wind turbine, or shutting down the wind turbine.

2. The method of claim 1 , wherein the slow variations in thrust of the tower are defined in a frequency domain, the slow variations being less than about 0.3 Hertz (Hz).

3. The method of claim 1 , wherein the tower loads comprise at least one of a tower deflection or a tower-base moment.

4. The method of claim 3 , wherein the tower deflection comprises a high bandwidth tower-top deflection which captures fast variations in thrust of the tower in the frequency domain of greater than about 0.3 Hertz (Hz).

5. The method of claim 4 , further comprising providing a 40 dB/decade drop from the tower accelerations to the estimated tower deflection between a frequency domain of from about 0.1 to 1 about Hertz (Hz).

6. The method of claim 4 , further comprising filtering, via a notch filter, the tower acceleration at the tower natural frequency.

7. The method of claim 4 , further comprising providing a 20 dB/decade drop from the tower accelerations to the estimated tower deflection between a frequency domain of from about 0.1 to 1 about Hertz (Hz).

8. The method of claim 4 , further comprising filtering, via a low-pass filter, from the estimate of slow variations in thrust of the tower to one or more controller outputs.

9. The method of claim 1 , wherein estimating the tower loads of the wind turbine as a function of the estimate of slow variations in thrust of the tower and the tower accelerations further comprises utilizing a Kalman filter.

10. The method of claim 1 , further comprising determining a tilt of the tower of the wind turbine and estimating the tower loads of the wind turbine, at least in part, as a function of the tilt.

11. A system comprising:

one or more sensors configured to measure tower accelerations of a tower of a wind turbine; and

a controller communicatively coupled with the one or more sensors, the controller comprising an estimator configured to perform one or more operations, the one or more operations comprising:

receiving an estimate of slow variations in thrust of the tower, wherein slow variations include variations in frequency lower than a tower natural frequency,

estimating the tower loads of the wind turbine as a function of the estimate of slow variations in thrust of the tower and the tower accelerations; and

initiating control actions for the wind turbine when the estimated tower loads are at a design limit, the control actions comprising at least one of controlling an operating mode of the wind turbine, starting up the wind turbine or shutting down the wind turbine.

12. The system of claim 11 , wherein the slow variations in thrust of the tower are defined in a frequency domain, the slow variations being less than about 0.3 Hertz (Hz).

13. The system of claim 11 , wherein the tower loads comprise at least one of tower-top deflection or tower-base moment.

14. The system of claim 13 , wherein the tower-top deflection comprises a high-bandwidth tower-top deflection which captures fast variations in wind speed and tower-top thrust in the frequency domain of greater than about 0.3 Hertz (Hz).

15. The system of claim 11 , wherein the one or more sensors comprise an accelerometer, wherein the accelerometer is configured to measure the tower accelerations of the tower.

16. The system of claim 11 , further comprising a Kalman filter, wherein the Kalman filter is configured to estimate the tower loads of the wind turbine as a function of the estimate of slow variations in thrust of the tower and the tower accelerations.

17. A method comprising:

estimating tower loads of a wind turbine by:

determining, via one or more sensors, an estimate of slow variations in thrust of a tower of the wind turbine, wherein slow variations include variations in frequency lower than a tower natural frequency;

determining, via one or more different sensors, an estimate of fast variations in thrust of a tower of the wind turbine, wherein estimate of fast variations include tower velocity of the tower; and

estimating, via the controller, the tower loads of the wind turbine as a function of the estimate of slow variations in thrust of the tower and the estimate of fast variations in thrust of the tower; and

providing tower damping to the tower, the tower damping comprising at least one of controlling an operating mode of the wind turbine, starting up the wind turbine or shutting down the wind turbine.

18. The method of claim 17 , wherein the slow variations in thrust of the tower are defined in a frequency domain, the slow variations being less than about 0.3 Hertz (Hz).

19. The method of claim 17 , wherein the tower loads comprise a high-bandwidth tower-top deflection which captures fast variations in thrust of the tower in the frequency domain of greater than about 0.3 Hertz.