Modular active structural vibration suppression for wind turbine blades

1. A system for reducing structural vibration on a wind turbine blade, the system comprising:

at least one flow control device (FCD) configured to be installed on a wind turbine blade, at least one of the at least one FCDs comprises a piezoelectric disk and a cavity, and the at least one FCD is capable of injecting momentum into a surrounding fluid through actuation of the piezoelectric disk;

at least one sensor configured to be installed on a wind turbine blade and to measure strain thereon; and

a closed loop control system in operable communication with the at least one FCD and the at least one sensor,

wherein the closed loop control system comprises a comparator for comparing information received from the at least one sensor to stored information about an acceptable load variation of a wind turbine blade, and

wherein an actuation frequency of the at least one FCD is chosen based on the dimensions of the cavity of the at least one FCD.

2. The system according to claim 1 , wherein the closed loop control system comprises a controller for controlling an input signal provided to the at least one FCD.

3. The system according to claim 2 , wherein the input signal is an amplitude of an input voltage.

4. The system according to claim 2 , wherein the controller controls the input signal by increasing it, decreasing it, or keeping it steady depending on information received from a comparator of the closed loop control system.

5. The system according to claim 2 , wherein the controller modulates, in the frequency domain, a carrier signal used to actuate the at least one FCD.

6. The system according to claim 1 , further comprising a wind turbine comprising a plurality of wind turbine blades, each wind turbine blade comprising at least one FCD and at least one sensor installed thereon.

7. The system according to claim 1 , wherein at least one of the at least one FCDs is a synthetic jet.

8. The system according to claim 1 , wherein at least one of the at least one FCDs is a vortex generator.

9. The system according to claim 1 , wherein at least one of the at least one sensors is a strain gauge.

10. The system according to claim 1 , wherein at least one of the at least one sensors is an accelerometer.

11. The system according to claim 1 , comprising an equal number of FCDs and sensors, wherein each sensor corresponds to and is in operable communication with an FCD, respectively.

12. The system according to claim 1 , wherein the at least one sensor provides information about the instantaneous deflection of the blade, on which the sensor is respectively installed, to the closed loop control system.

13. The system according to claim 12 , wherein the at least one sensor provides time history information about the amplitude of recent time deflections of the blade to the closed loop control system, and

wherein the at least one sensor provides information about a derivative of a time variance of the deflection of the blade to the closed loop control system.

14. The system according to claim 12 , wherein the at least one sensor provides information continuously to the closed loop control system.

15. The system according to claim 12 , wherein the closed loop control system uses information provided by the at least one sensor to determine whether and how much to change an input signal to the at least one FCD.

16. The system according to claim 1 , wherein, if a wind turbine blade has an increase in load variation in time, the closed loop control system actuates the at least one FCD such that lower variations in load oscillation amplitude result.

17. A method for reducing structural vibration on a wind turbine blade, the method comprising:

installing the system according to claim 1 on a wind turbine; and

using the system to reduce structural vibration on wind turbine blades of the wind turbine.

18. A system for reducing structural vibration on a wind turbine blade, the system comprising:

at least one flow control device (FCD) configured to be installed on a wind turbine blade;

at least one sensor configured to be installed on a wind turbine blade and to measure strain thereon; and

a closed loop control system in operable communication with the at least one FCD and the at least one sensor,

wherein the closed loop control system comprises a comparator for comparing information received from the at least one sensor to stored information about an acceptable load variation of a wind turbine blade,

wherein the at least one sensor provides information about the instantaneous deflection of the blade, on which the sensor is respectively installed, to the closed loop control system,

wherein the at least one sensor provides time history information about the amplitude of recent time deflections of the blade to the closed loop control system, and

wherein the at least one sensor provides information about a derivative of a time variance of the deflection of the blade to the closed loop control system.

19. The system according to claim 18 , wherein the at least one sensor provides information continuously to the closed loop control system.

20. The system according to claim 18 , wherein the closed loop control system uses information provided by the at least one sensor to determine whether and how much to change an input signal to the at least one FCD.

21. The system according to claim 18 , wherein, if a wind turbine blade has an increase in load variation in time, the closed loop control system actuates the at least one FCD such that lower variations in load oscillation amplitude result.