Horizontal axis wind turbine and method for controlling horizontal axis wind turbine

1. A horizontal axis wind turbine comprising:

a yaw sensor;

a rotor rotating around a rotor axis extending in a substantially horizontal direction, the rotor axis rotating in a substantially horizontal plane depending on yaw angle;

a plate-like member disposed on a rotational central portion of the rotor and extending in a parallel direction to the rotor axis and in a vertical direction;

two anemometers disposed at positions which are across the plate-like member; and

a controller for yaw control based on wind speeds measured by the two anemometers.

2. The wind turbine as claimed in claim 1 , wherein the controller estimates a yaw angle of the rotor based on the difference or the ratio between the wind speeds measured by the two anemometers, and rotates the rotor axis so that the estimated yaw angle converges to about 0 degree.

3. A method for controlling the wind turbine as claimed in claim 1 , the method comprising:

estimating the yaw angle based on the wind speeds measured by the two anemometers; and

rotating the rotor axis so that the estimated yaw angle converges to about 0 degree.

4. A method for controlling the wind turbine as claimed in claim 1 , the method comprising:

determining whether the difference between the wind speeds measured by the two anemometers is more than a predetermined threshold or not;

rotating the rotor axis to one anemometer which measures a higher wind speed than other anemometer when the difference between the wind speeds exceeds the threshold; and

stopping rotation of the rotor axis when the difference between the wind speeds falls not more than the threshold.

5. A horizontal axis wind turbine comprising:

a rotor for rotating around a rotor axis extending in a substantially horizontal direction;

two anemometers;

a parting member disposed so that wind speeds measured by the anemometers are different except when a yaw angle of the rotor is substantially 0 degree; and

a controller for controlling the yaw angle of the rotor based on the wind speeds measured by the two anemomoters.

6. The wind turbine as claimed in claim 5 , further comprising a yaw sensor.

7. The wind turbine as claimed in claim 5 , wherein the parting member is a plate-like member.

8. The wind turbine as claimed in claim 5 , wherein the controller controls the yaw angle based on a difference between the wind speeds measured by the two anemometers.

9. The wind turbine as claimed in claim 5 , wherein the controller controls the yaw angle of the rotor based on a ratio between the wind speeds measured by the two anemometers.

10. The wind turbine as claimed in claim 5 , wherein the controller compares the wind speeds measured by the two anemometers and rotates the rotor axis to one anemometer which measures a higher wind speed than other anemometer.

11. The wind turbine as claimed in claim 5 , wherein the controller calculates a control determination value from the wind speeds measured by the two anemometers, determines whether the control determination value is within a predetermined range or not, rotates the rotor axis to an anemometer which measures a higher wind speed than other anemometer when the control determination value is out of the predetermined range, and stops rotation of the rotor axis when the control determination value comes within the range.

12. The wind turbine as claimed in claim 11 , wherein a difference or a ratio between wind speeds measured by the two anemometers is used as the control determination value.

13. The wind turbine as claimed in claim 5 , wherein the controller estimates the yaw angle of the rotor based on the wind speeds measured by the two anemometers, and rotates the rotor axis so that the estimated yaw angle converges to about 0 degree.

14. The wind turbine as claimed in claim 5 , wherein the controller comprises:

a wind speed difference calculation unit for calculating a wind speed difference from wind speeds measured by the two anemometers;

a recording unit for recording wind speed difference correlation data showing relationship between the wind speed difference and the yaw angle;

a yaw angle estimation unit for estimating the yaw angle by using the wind speed difference calculated by the wind speed difference calculation unit and the wind speed difference correlation data recorded in the recording unit; and

a yaw control unit for rotating the rotor axis so that the estimated yaw angle converges to about 0 degree.

15. The wind turbine as claimed in claim 5 , wherein the controller comprises:

a wind speed ratio calculation unit for calculating a wind speed ratio from wind speeds measured by the two anemometers;

a recording unit for recording wind speed ratio correlation data showing relationship between the wind speed ratio and the yaw angle;

a yaw angle estimation unit for estimating the yaw angle by using the wind speed ratio calculated by the wind speed ratio calculation unit and the wind speed ratio correlation data recorded in the recording unit; and

a yaw control unit for rotating the rotor axis so that the estimated yaw angle converges to about 0 degree.

16. A method for controlling the wind turbine as claimed in claim 5 , the method comprising:

comparing the wind speeds measured by the two anemometers; and

rotating the rotor axis to an anemometer which measures a higher wind speed than other anemometer.

17. A method for controlling the wind turbine as claimed in claim 5 , the method comprising:

calculating a control determination value from wind speeds measured by the two anemometers;

determining whether the control determination value is within a predetermined range or not;

rotating the rotor axis to an anemometer which measures a higher wind speed than other anemometer when the control determination value is out of the predetermined range; and

stopping rotation of the rotor axis when the control determination value comes in the range.

18. The method for controlling the wind turbine as claimed in claim 17 , wherein a difference or a ratio between wind speeds measured by the two anemometers is used as the control determination value.

19. A method for controlling the wind turbine as claimed in claim 5 , the method comprising:

measuring the wind speeds by the two anemometers;

calculating a wind speed difference from the wind speeds measured by the two anemometers;

estimating the yaw angle by using the wind speed difference calculated by the wind speed difference calculation unit and wind speed difference correlation data showing relationship the wind speed difference and the yaw angle; and

rotating the rotor axis so that the estimated yaw angle converges to about 0 degree.

20. A method for controlling the wind turbine as claimed in claim 5 , the method comprising:

measuring the wind speeds by the two anemometers;

calculating a wind speed ratio from the wind speeds measured by the two anemometers;

estimating the yaw angle by using the wind speed ratio calculated by the wind speed ratio calculation unit and wind speed ratio correlation data showing relationship the wind speed ratio and the yaw angle; and

rotating the rotor axis so that the estimated yaw angle converges to about 0 degree.