Wind turbine control

1. A method for controlling a wind turbine with variable speed and blade pitch angle control, the method comprising:

receiving a first signal indicative of a wind power;

receiving a second signal indicative of wind turbulence intensity;

obtaining a first control parameter indicative of foreseeable fluctuations in a rotational speed of a rotor based on the first signal indicative of the wind power and the second signal indicative of the wind turbulence intensity;

comparing the first control parameter with a first threshold value;

foreseeing fluctuations in a rotational speed of a rotor based on the comparison of the first control parameter with the first threshold value; and

reducing a maximum power to be generated by the wind turbine if the first control parameter exceeds said first threshold value.

2. The method of claim 1 , wherein the first signal indicative of the wind power is obtained from a value resulting from cubing of a third signal indicative of the wind.

3. The method of claim 2 , wherein the second signal indicative of wind turbulence intensity is obtained from a deviation between the third signal indicative of the wind and an average of the third signal indicative of the wind over a period of time.

4. The method of claim 3 , wherein the third signal indicative of the wind comprises a blade pitch angle.

5. The method of claim 3 , wherein the third signal indicative of the wind comprises a measurement of an anemometer situated on the turbine's nacelle when the wind turbine is stopped.

6. The method of claim 5 , further comprising using the first control parameter in order to calculate the maximum power to be generated by the turbine following a start-up.

7. The method of claim 1 , further comprising:

obtaining a second control parameter indicative of a severity of a change in wind speed, the second control parameter being calculated as an integral of an absolute value of a derivative of a third signal indicative of the wind;

comparing the second control parameter with a second threshold value; and

reducing the maximum power to be generated by the wind turbine if the second control parameter exceeds the second threshold value.

8. The method of claim 7 , wherein the third signal indicative of the wind power comprises the blade pitch angle.

9. The method of claim 1 , wherein reducing the maximum power to be generated by the wind turbine comprises reducing a nominal speed of rotation of a rotor.

10. The method of claim 9 , wherein reducing the maximum power to be generated by the wind turbine comprises increasing the minimum blade pitch angle.

11. The method of claim 10 , wherein reducing the maximum power to be generated by the wind turbine comprises, in a high winds regime when a rotor's rotational speed is limited by controlling the blade pitch angle, maintaining the torque required of a generator substantially constant.

12. The method of claim 1 , further comprising:

obtaining a third control parameter indicative of the wind speed based on the blade pitch angle;

comparing the third control parameter with a third threshold value; and

activating a shutdown manoeuvre if the third control parameter exceeds the third threshold value.

13. The method of claim 12 , further comprising verifying a correlation between the blade pitch angle and a third signal indicative of the wind impacting on the wind turbine obtained from at least one anemometer.

14. The method of claim 13 , wherein activating the shutdown manoeuvre comprises activating the shutdown manoeuvre if the correlation is not verified.

15. The method of claim 13 , wherein the third signal indicative of the wind is provided by a central control which calculates the third signal based on at least one anemometer situated on a wind turbine or nearby meteorological tower.

16. The method of claim 1 , further comprising:

obtaining a second control parameter indicative of a severity of a change in wind speed, the second control parameter being calculated as an integral of an absolute value of a derivative of a third signal indicative of the wind,

comparing the second control parameter with a second threshold value, and

if the second control parameter exceeds the second threshold value, performing at least one of the following: reducing the maximum power to be generated by the wind turbine, reducing the rotational speed of a rotor, and modifying a dynamic of a speed and power of control loops.

17. The method of claim 1 , wherein the control parameter is calculated as a product of the first signal indicative of wind power multiplied by the second signal indicative of wind turbulence intensity.

18. A method for controlling a wind turbine with variable speed and blade pitch angle control, the method comprising:

obtaining a control parameter indicative of foreseeable fluctuations in a rotational speed of a rotor based on a first signal indicative of wind power and a second signal indicative of wind turbulence;

comparing the control parameter with a threshold value;

foreseeing fluctuations in the rotational speed of the rotor based on the comparison of the first control parameter with the threshold value; and

if the control parameter exceeds the threshold value, performing at least one of the following:

reducing a maximum power to be generated by the wind turbine, reducing the rotational speed of the rotor, and

modifying a dynamic of a speed and power of control loops.

19. The method of claim 18 , wherein the first signal indicative of the wind power is obtained from a value resulting from cubing of a third signal indicative of the wind.

20. The method of claim 19 , wherein the second signal indicative of wind turbulence intensity is obtained from a deviation between the third signal indicative of the wind and an average of the third signal indicative of the wind over a period of time.

21. The method of claim 18 , wherein the control parameter is calculated as a product of the first signal indicative of wind power multiplied by the second signal indicative of wind turbulence.

22. A wind turbine comprising:

a rotor;

a blade pitch adjustment system; and

a calculating unit, wherein the calculating unit is operative to:

calculate a control parameter as a product of a first signal indicative of wind power multiplied by a second signal indicative of wind turbulence, the control parameter indicative of foreseeable fluctuations in a rotational speed of the rotor,

compare the control parameter with a threshold value, and

reduce a maximum power to be generated by the wind turbine if the control parameter exceeds the threshold value.

23. The wind turbine of claim 22 , wherein the calculating unit is further operative to reduce the rotational speed of the rotor if the control parameter exceeds the threshold value.

24. A wind turbine comprising:

a rotor,

a blade pitch adjustment system, and

a calculating unit,

wherein the calculating unit is operative to:

obtain a control parameter indicative of foreseeable fluctuations in a rotational speed of the rotor, the control parameter being calculated as a product of a first signal indicative of wind power multiplied by a second signal indicative of wind turbulence;

compare the control parameter with a threshold value; and

if the control parameter exceeds the threshold value, the calculating unit being further operative to perform at least one of the following:

reduce a maximum power to be generated by the wind turbine,

reduce the rotational speed of the rotor, and

modify a dynamic of a speed and power of control loops.