Method of operating a wind turbine and wind turbine

1. A method of operating a wind turbine having a rotor, comprising:

determining a wind speed;

determining an average wind speed;

determining a deviation of the wind speed from the average wind speed;

comparing the deviation of the wind speed with a threshold value; and

when the deviation of the wind speed from the average wind speed attains or exceeds a threshold value reducing

a rotor rotational speed, or

an electrical power output of the wind turbine or

both the rotor rotational speed and the electrical power output of the wind turbine as a function of the deviation of the wind speed from the average wind speed.

2. The method according to claim 1 , wherein the deviation of the wind speed from the average wind speed is determined as a standard deviation.

3. The method according to claim 1 , wherein the deviation of the wind speed from the average wind speed is iterative determined in consideration of the average wind speed and the instantaneous wind speed.

4. The method according to claim 1 , wherein the deviation of the wind speed from the average wind speed is determined according to the following equations:

D n =C ·num( V inst,n −V av,n )+(1− C )· D n-1   (1)

V av,n =C·V inst,n +(1− C )· V av,n-1   (2)

with

Dn deviation sum at the n′th calculation step,

Dn−1 deviation sum at the previous calculation step,

Vav,n average wind speed at the n′th calculation step,

Vav,n−1 average wind speed at the previous calculation step,

Vinst,n instantaneous wind speed at the n′th calculation step,

C constant being a number between 0 and 1 and

num numerical value.

5. The method according to claim 1 , wherein the rotational speed of the rotor and/or the electrical power output are reduced in consideration of a further meteorological parameter.

6. The method according to claim 5 , wherein the further meteorological parameter is the deviation of the wind direction from the average wind direction.

7. The method according to claim 6 , wherein the deviation of the wind direction from the average wind direction is determined as a standard deviation.

8. The method according to claim 5 , further comprising determining a load value.

9. The method according to claim 8 , wherein the relation of the load value and the meteorological parameter is determined by simulation and/or by field measurement of loading.

10. The method according to claim 9 , wherein the relation of the load value and the meteorological parameter is determined in an adjusting process based on a measurement value acquired by a transducer.

11. The method according to claim 10 , wherein the transducer is an accelerometer or a strain gauge.

12. The method according to claim 11 , wherein the rotational speed of the rotor and/or the electrical power output of the wind turbine are reduced, when the load value attains or exceeds a threshold load value.

13. The method according to claim 12 , wherein the rotational speed of the rotor and/or the electrical power output of the wind turbine are reduced as a function of the load value.

14. A wind turbine, comprising:

a tower;

a nacelle arranged upon the tower, wherein the tower supports the nacelle;

a rotor rotatably arranged within the nacelle, wherein the rotor has a hub and a plurality of pitch controlled rotor blades;

an electric generator connected to and driven by the rotor;

a measuring device that measures a wind speed; and

a calculating unit that:

determines an average wind speed;

determines a deviation of the wind speed from the average wind speed;

compares the deviation of the wind speed with a threshold value; and

when the deviation of the wind speed from the average wind speed attains or exceeds a threshold value, reduces

a rotor rotational speed, or

an electrical power output of the wind turbine or

both the rotor rotational speed and the electrical power output of the wind turbine as a function of the deviation of the wind speed from the average wind speed.