Tilt damping of a floating wind turbine

1. A method for use with a wind turbine comprising a nacelle, the method comprising:

determining a gain scheduling parameter based on at least a received operating point signal describing an operating point of the wind turbine;

receiving an input signal describing motion of the nacelle;

generating a signal proportional to a velocity of the nacelle determined based on said input signal;

generating a tilt damping signal by multiplying said signal proportional to said velocity by said determined gain scheduling parameter; and

modifying a control signal for a system of the wind turbine using the tilt damping signal.

2. The method as claimed in claim 1 , wherein modifying the control signal for a system of the wind turbine comprises:

modifying a pitch demand signal for a pitch control system of the wind turbine.

3. The method as claimed in claim 1 , in which said input signal is a nacelle velocity signal.

4. The method as claimed in claim 1 , in which said input signal is an acceleration signal, wherein said acceleration signal includes acceleration measurements relating to the nacelle, and generating said signal proportional to said velocity comprises:

integrating said acceleration signal using an anti-wind-up leaky integrator.

5. The method according to claim 1 , further comprising:

filtering said received input signal to at least substantially reduce one or more frequency components that are unrelated to a natural frequency of a floating platform connected with the wind turbine.

6. A method for use with a floating wind turbine, the method comprising:

determining a gain scheduling parameter based on at least a received operating point signal describing an operating point of the floating wind turbine;

receiving an acceleration signal describing an acceleration of the floating wind turbine;

multiplying said acceleration signal by said determined gain scheduling parameter to generate a gain-scheduled acceleration signal; and

generating, using a turbine controller of the floating wind turbine, a pitch demand signal for a pitch control system of the floating wind turbine, the pitch demand signal comprising a tilt damping component based on the gain-scheduled acceleration signal and a generator speed error signal.

7. The method as claimed in claim 6 , further comprising:

multiplying said gain-scheduled acceleration signal by a further gain parameter that is based on one or more gains applied in said turbine controller.

8. The method as claimed in claim 6 , further comprising:

combining said gain-scheduled acceleration signal with said generator speed error signal in a combined signal; and

integrating said combined signal to generate said pitch demand signal.

9. The method as claimed in claim 6 , further comprising:

combining said generated pitch demand signal with a gain-scheduled generator speed error signal.

10. The method as claimed in claim 6 , further comprising:

multiplying said generated pitch demand signal by a gain parameter.

11. The method according to claim 6 , further comprising:

filtering said received acceleration signal to at least substantially reduce one or more frequency components unrelated to a natural frequency of a floating platform of the floating wind turbine.

12. The method as claimed in claim 6 , further comprising:

filtering and time delaying said operating point signal.

13. The method as claimed in claim 6 , in which said operating point signal is a pitch angle signal.

14. The method according to claim 6 , in which determining said gain scheduling parameter comprises:

identifying said gain scheduling parameter from a predefined lookup table relating said operating point to gain scheduling parameter.

15. An apparatus comprising:

a first input configured to receive an operating point signal describing an operating point of a wind turbine;

a second input configured to receive an input signal describing motion of a nacelle of the wind turbine;

a component configured to generate a signal proportional to a velocity of the nacelle determined based on said input signal; and

a gain scheduling component configured to:

determine a gain scheduling parameter based on at least said received operating point signal; and

multiply said signal proportional to said velocity by said determined gain scheduling parameter to generate a tilt damping signal,

wherein a control signal for a system of the wind turbine is modified using the tilt damping signal.

16. The apparatus as claimed in claim 15 , further comprising:

a combiner configured to modify a pitch demand signal for a pitch control system of the wind turbine.

17. The apparatus as claimed in claim 15 , in which said input signal is a nacelle velocity signal.

18. The apparatus as claimed in claim 15 , in which said input signal is an acceleration signal, wherein said acceleration signal includes acceleration measurements relating to the nacelle, and said component configured to generate said signal proportional to said velocity comprises:

an anti-wind-up leaky integrator configured to integrate said acceleration signal.

19. The apparatus as claimed in claim 15 , further comprising:

a filter configured to filter said received input signal to at least substantially reduce one or more frequency components that are unrelated to a natural frequency of a floating platform connected with the wind turbine.

20. The apparatus as claimed in claim 15 , further comprising:

a filter configured to filter and time delay said operating point signal.

21. The apparatus as claimed in claim 15 , in which said operating point signal is a pitch angle signal.

22. The apparatus as claimed in claim 15 , in which said gain scheduling component is configured to:

identify said gain scheduling parameter from a predefined lookup table relating said operating point to gain scheduling parameter.

23. An apparatus comprising:

a first input configured to receive an operating point signal describing an operating point of a floating wind turbine;

a second input configured to receive an acceleration signal describing an acceleration of the floating wind turbine;

a gain scheduling component configured to:

determine a gain scheduling parameter based on at least said received operating point signal; and

multiply said acceleration signal by said determined gain scheduling parameter to generate a gain-scheduled acceleration signal; and

an output configured to transmit said gain-scheduled acceleration signal to a turbine controller of said floating wind turbine,

wherein the turbine controller is configured to generate a pitch demand signal for a pitch control system of the floating wind turbine, the pitch demand signal comprising a tilt damping component based on at least said gain-scheduled acceleration signal and a generator speed error signal.

24. The apparatus as claimed in claim 23 , further comprising:

a gain component configured to multiply said gain-scheduled acceleration signal by a further gain parameter that is based on one or more gains applied in said turbine controller.

25. The apparatus as claimed in claim 23 , further comprising:

a first combiner configured to combine said gain-scheduled acceleration signal with said generator speed error signal in a combined signal; and

an integrator configured to integrate said combined signal to generate said pitch demand signal.

26. The apparatus as claimed in claim 23 , further comprising:

a second combiner configured to combine said generated pitch demand signal with a gain-scheduled generator speed error signal.

27. The apparatus as claimed in claim 23 , further comprising:

a gain component configured to multiply said generated pitch demand signal by a gain parameter.

28. The apparatus as claimed in claim 23 , further comprising:

a filter configured to at least substantially reduce, from the acceleration signal, one or more frequency components that unrelated to a natural frequency of a floating platform of the floating wind turbine.