SYSTEM AND METHOD FOR IDENTIFYING THE LIKELIHOOD OF A TOWER STRIKE WHERE A ROTOR BLADE STRIKES THE TOWER OF A WIND TURBINE

• US 20130287567A1
• Filed: 10/31/2011
• Published: 10/31/2013
• Est. Priority Date: 11/02/2010
• Status: Active Grant

• Current Assignee: Vestas Wind Systems A/S
• Original Assignee: Vestas Wind Systems A/S
• Inventors: Olesen, Ib Svend, Glavind, Lars
• Granted Patent: US 9,347,435 B2
• Time in Patent Office: Days
• US Class Current: 416/1
• CPC Class Codes: F03D 17/00 Monitoring or testing of wind motors, e.g. diagnostics testing during commissioning of wind motors F03D13/30
• CPC Class Codes: F03D 7/0288 in relation to clearance between the blade and the tower, i.e. preventing tower strike
• CPC Class Codes: F05B 2240/912 on a tower
• CPC Class Codes: F05B 2270/17 to avoid excessive deflection of the blades
• CPC Class Codes: F05B 2270/33 Proximity of blade to tower
• CPC Class Codes: F05B 2270/804 Optical devices
• CPC Class Codes: F05B 2270/808 Strain gauges; Load cells
• CPC Class Codes: F05B 2270/821 Displacement measuring means, e.g. inductive
• CPC Class Codes: Y02E 10/72 Wind turbines with rotation axis in wind direction
• CPC Class Codes: Y02E 10/728 Onshore wind turbines

Abstract

A system for identifying the likelihood of a wind turbine rotor blade striking a wind turbine tower comprises a device for sensing bending of a wind turbine rotor blade and a device for sensing bending of a wind turbine tower. In a preferred embodiment Long Period Grating (LPG) sensors are used to measure bending of the tower. Preferably a plurality of LPG sensors is provided along the length of the blade. In one embodiment at least one of the LPG sensors comprises two sensing elements arranged to sense in perpendicular directions. In another embodiment a plurality of LPG sensors are provided each on different sides of the wind turbine tower. A processor uses the sensed blade and tower bending to determine whether the distance between the blade and the tower will be below a predetermined minimum value. If the distance is determined to be below the predetermined minimum value a controller may be used to adjust a wind turbine variable to reduce loading on the blade and thereby reduce the likelihood of a tower strike.

Claims

1. A wind turbine comprising:

at least one rotor blade and a tower;

a device for sensing bending of the rotor blade;

a device for sensing bending of the tower; and

a processor for determining, using the sensed blade and tower bending, whether a distance between the blade and the tower will be below a predetermined minimum value.

2. A wind turbine according to claim 1, wherein the device for sensing bending of the rotor blade comprises a sensor arranged at the blade for outputting a signal indicative of blade bending;

and an analyser configured to determine a measurement of blade bending based on the signal.

3. A wind turbine according to claim 2, wherein the sensor is arranged to measure bending of the blade at least in the region of the blade tip.

4. A wind turbine according to claim 1, wherein the device for sensing bending of the tower comprises a sensor arranged at the tower for outputting a signal indicative of tower bending;

and an analyser configured to determine a measurement of tower bending based on the signal.

5. A wind turbine according to claim 4, wherein the sensor is mounted on or embedded in the tower.

6. A wind turbine according to claim 4, wherein the sensor comprises an optical fibre having an optical grating.

7. A wind turbine according to claim 6, wherein the sensor comprises a Long Period Grating sensor.

8. A wind turbine according to claim 7, wherein the device for sensing bending of the tower further comprises a light emitting device arranged to input a light signal into the optical fibre of the Long Period Grating sensor and a light collecting device arranged to receive the light signal that has passed through the optical fibre of the Long Period Grating sensor.

9. A wind turbine according to claim 7, wherein the Long Period Grating sensor comprises an optical fibre having a plurality of optical gratings.

10. A wind turbine according to claim 9, wherein the optical fibre has two optical gratings arranged for measuring bend of the tower in perpendicular directions.

11. A wind turbine according to claim 4, comprising a plurality of sensors each for outputting a signal indicative of tower bending;

the analyser being configured to determine a measurement of tower bending based on the signals.

12. A wind turbine according to claim 11, wherein at least two of the sensors are spaced along the tower.

13. A wind turbine according to claim 11, wherein at least two of the sensors are spaced around at least a portion of the circumference of the tower.

14. A wind turbine according to claim 1, wherein the wind turbine comprises a nacelle and the processor is configured to determine tilt of the nacelle based on the sensed bending of the tower, wherein the determined tilt of the nacelle is used by the processor when determining whether the distance between the blade and the tower will be below a predetermined minimum value.

15. A wind turbine according to claim 10, wherein the wind turbine comprises a nacelle arranged to rotate the at least one rotor blade about the longitudinal axis of the tower;

and the processor uses a determination of tower bending in the direction the rotor blade will be when it passes the tower for determining whether the distance between the rotor blade and the tower will be below a predetermined minimum value.

16. A wind turbine according to claim 1, wherein the wind turbine further comprises a nacelle arranged to rotate the at least one rotor blade with respect to the longitudinal axis of the tower;

and the processor uses knowledge of the rotation of the rotor blade when determining whether the distance between the rotor blade and the tower will be below a predetermined minimum value.

17. A wind turbine according to claim 16 further comprising a sensor for detecting nacelle orientation, the processor using a signal indicative of nacelle orientation in said distance determination.

18. A wind turbine according to claim 1, comprising a controller for adjusting a variable of the wind turbine to reduce the loading on the rotor blade when the processor determines that the distance between the blade and the tower will be below a predetermined minimum value.

19. A wind turbine according to claim 18, wherein the variable is the pitch of the rotor blade.

20. A wind turbine power plant, comprising:

a plurality of wind turbines having a tower and at least one rotor blade, wherein at least one of the wind turbines comprises;

at least one rotor blade and a tower;

a device for sensing bending of the rotor blade;

a device for sensing bending of the tower; and

a processor for determining, using the sensed blade and tower bending,

whether a distance between the blade and the tower will be below a predetermined minimum value; and

a controller for sending a signal to adjust a variable of at least one of the plurality of wind turbines to reduce the loading on the rotor blade of the wind turbine when the processor determines that the distance between the blade and the tower will be below a predetermined minimum value.

21. A method of operating a wind turbine, comprising:

sensing bending of a rotor blade using the device;

sensing bending of a tower using the device; and

determining, using the sensed blade and tower bending, whether a distance between the blade and the tower will be below a predetermined minimum value.

22. A method according to claim 21, wherein the wind turbine comprises a nacelle arranged to rotate the at least one rotor blade about the longitudinal axis of the tower;

and the step of determining whether the distance between the blade and the tower will be below a predetermined minimum value comprises using a determination of tower bending in the direction the rotor blade will be when it passes the tower.

23. A method according to claim 21, wherein the wind turbine further comprises a nacelle arranged to rotate the at least one rotor blade with respect to the longitudinal axis of the tower;

and the step of determining whether the distance between the blade and the tower will be below a predetermined minimum value comprises using knowledge of the rotation of the rotor blade.

24. A method according to claim 21, further comprising operating a controller to adjust a variable of the wind turbine to reduce the loading on the rotor blade upon determining that the distance between the blade and the tower will be below a predetermined minimum value.

25. A method according to claim 24, wherein the variable is the pitch of the rotor blades.

26. (canceled)