Yaw control system and yaw control method for wind turbine generator

1. A yaw control system for a wind turbine generator which includes a nacelle

configured to be rotated by a yaw drive mechanism, the yaw control system comprising:

a yaw direction sensor for detecting a yaw direction value of the nacelle at a current time; and

a controller including a processor and a memory and configured to control the yaw drive mechanism,

wherein the controller is configured to:

calculate an amount of yaw rotation of the nacelle in a predetermined period of time based on a yaw rotation speed and a yaw rotation time of the nacelle; and

calculate an estimate value of a yaw direction of the nacelle at an end point of the predetermined period by an estimate value calculation logic, based on the amount of yaw rotation in the predetermined period and the yaw direction value at a starting point of the predetermined period, and

wherein the controller is configured to:

when the yaw direction sensor is normal, determine a yaw rotation direction of the nacelle based on a detected result of the yaw direction value detected by the yaw direction sensor, generate a first yaw rotation command based on the determined yaw rotation direction, and send the first yaw rotation command to the yaw drive mechanism; and

when the yaw direction sensor is abnormal, determine the yaw rotation direction of the nacelle based on the estimate value of the yaw direction, generate a second yaw rotation command based on the determined yaw rotation direction, and send the second yaw rotation command to the yaw drive mechanism.

2. The yaw control system for a wind turbine generator according to claim 1 , further comprising

a wind direction sensor for detecting a wind direction of a wind which acts on the wind turbine generator,

wherein the controller is configured to rotate the nacelle in the yaw rotation direction based on a detected result of the wind direction sensor so that the nacelle follows the wind direction detected by the wind direction sensor.

3. The yaw control system for a wind turbine generator according to claim 1 ,

wherein the controller is configured to correct the estimate value calculation logic based on a comparison result between the yaw direction value detected by the yaw direction sensor when the yaw direction sensor is normal and the estimate value of the yaw direction calculated when the yaw direction sensor is normal.

4. The yaw control system for a wind turbine generator according to claim 3 ,

wherein the controller is configured is configured to:

calculate the estimate value of the yaw direction from a correlation of the yaw direction value at the end point of the predetermined period to the yaw direction value at the starting point of the predetermined period and the amount of yaw rotation in the predetermined period, and

correct the correlation based on the comparison result.

5. The yaw control system for a wind turbine generator according to claim 1 ,

wherein the controller is configured to calculate the estimate value of the yaw direction from a correlation of the yaw direction value at the end point of the predetermined period to the yaw direction value at the starting point of the predetermined period and the amount of yaw rotation in the predetermined period, and

the correlation is set for each yaw rotation direction of the nacelle.

6. The yaw control system for a wind turbine generator according to claim 1 ,

wherein the controller is configured to, when the yaw direction sensor is abnormal, correct the estimate value based on a reference yaw direction value detected by a normal yaw direction sensor of another wind turbine generator which is under wind conditions similar to the wind turbine generator.

7. The yaw control system for a wind turbine generator according to claim 6 ,

wherein the controller is configured to correct the estimate value based on the reference yaw direction value once a difference between: an amount of change of the estimate value of the yaw direction calculated in a set period; and an amount of change of the reference yaw direction value in the set period exceeds a threshold value.

8. A wind turbine generator comprising: a yaw control system according to claim 1 ; a yaw drive mechanism configured to be controlled by the yaw control system; and a nacelle configured to be rotated by the yaw drive mechanism.