Method and system for calibrating a wind vane

1. A method for calibrating a wind vane of a wind turbine that is arranged, together with two anemometers, on a leeward side of a rotor of the wind turbine, comprising:

measuring a first wind speed by means of a first anemometer, a second wind speed by means of a second anemometer, and a wind direction by means of the wind vane, a multiplicity of measurement values being recorded over a defined time period;

determining differences between the first wind speed and the second wind speed at least substantially at the same instants in each case; determining a model function for a relationship between the measured wind directions and the determined differences that correspond at least substantially to the same instants, at least one first model function being determined for a first wind-speed bin and at least one second model function being determined for a second wind-speed bin;

determining at least one intersection point value of the measured wind direction at which the first model function and the second model function intersect;

outputting the intersection point value as an installation angle of the wind vane.

2. The method according to claim 1 , a model on which the model function is based being linear.

3. The method according to claim 1 , the model function being determined on the basis of a compensation calculation.

4. The method according to claim 1 , more than two model functions being determined, and the installation angle of the wind vane being output as a mean value from a plurality of determined intersection point values of the measured wind direction, at which respectively two model functions for different wind-speed bins intersect.

5. The method according to claim 1 , the multiplicity of measurement values generated by the first anemometer being corrected with a first correction function, for the purpose of measuring the first wind speed, and/or the multiplicity of measurement values generated by the second anemometer being corrected with a second correction function, for the purpose of measuring the second wind speed.

6. A method for monitoring a wind turbine having a wind vane that, together with two anemometers, is arranged on a leeward side of a rotor of the wind turbine, comprising:

cyclically executing the method according to claim 1 ;

determining a calibration quality on the basis of a time progression of the cyclically output installation angle.

7. A method for operating a wind turbine having a nacelle, arranged on a tower, a rotor and a wind vane that is arranged, together with two anemometers, on a leeward side of the rotor, which comprises:

ascertaining an installation angle by means of the method according to claim 1 ;

adjusting the wind vane on the basis of the output installation angle; and

aligning the nacelle on the basis of wind directions measured by means of the adjusted wind vane.

8. A non-transitory computer-readable medium, with computer-executable instructions stored thereon for executing the steps of a method according to claim 1 .

9. A method for calibrating a wind vane of a wind turbine that is arranged, together with two anemometers, on a leeward side of a rotor of the wind turbine, comprising:

measuring a first wind speed by means of a first anemometer, a second wind speed by means of a second anemometer, and a wind direction by means of the wind vane, a multiplicity of measurement values being recorded over a defined time period;

determining differences between the first wind speed and the second wind speed at least substantially at the same instants in each case; determining a model function for a relationship between the measured wind directions and the determined differences that correspond at least substantially to the same instants, for a wind-speed bin;

determining a value of the measured wind direction at which the model function assumes a predefined difference value; and

outputting the determined value as an installation value of the wind vane.

10. A system for calibrating a wind vane of a wind turbine having a wind vane for measuring a wind direction, a first anemometer for measuring a first wind speed, a second anemometer for measuring a second wind speed, and a control facility, the wind vane, the first anemometer and the second anemometer being arranged on a leeward side of a rotor of the wind turbine, and the control facility having:

means for recording a multiplicity of measurement values of the first and second anemometers and of the wind vane over a predefined time period;

means for determining differences between the first wind speed and the second wind speed at respectively at least substantially the same instants;

means for determining a first model function for a first relationship between wind directions, measured by means of the wind vane, and determined differences that correspond, at least substantially, to the same instants, for a first wind-speed bin;

means for determining a second model function for a second relationship between wind directions, measured by means of the wind vane, and determined differences that correspond, at least substantially, to the same instants, for a second wind-speed bin;

means for determining at least one intersection point value of the measured wind direction at which the first model function and the second model function intersect; and

an interface, which is configured to output the at least one determined intersection point value as an installation angle of the wind vane.

11. The system according to claim 10 , the first anemometer and the second anemometer being arranged, together with the wind vane, in a plane perpendicular to a rotor axis of the rotor.

12. The system according to claim 10 , the first anemometer and the second anemometer being arranged at a distance from each other, and the first anemometer and the second anemometer being arranged with an offset in a horizontal direction that is substantially perpendicular to a direction of a gravitational vector.

13. The system according to claim 12 , wherein the first anemometer and the second anemometer are equidistant in relation to the wind vane.

14. The system according to claim 10 , the first anemometer being realized so as to be structurally identical to the second anemometer.