The wind turbine yaw control system provides two functions that are crucial to safe and efficient operation:
- Wind direction orientation
- Cable twist control
The nacelle must point directly into the wind for maximum efficiency. Also, a rotor disk that is not perpendicular to the relative wind experiences higher loading on the portion of the disk that is closest to the wind. This can lead to accelerated fatigue of the blades.
Yaw control is based on input from the wind vane or sonic anemometer, which senses wind direction, as well as input from the yaw position sensor which tracks the nacelle position.
The controller uses these inputs to calculate misalignment or yaw error.
When the yaw error rises to a trigger value, the controller signals the yaw brake to release and commands the yaw motors to begin turning the nacelle. When the nacelle is properly aligned, the motors shut off and the yaw brake is applied.
The system also counts the revolutions of the nacelle to determine the number of twists in the cables that run down the tower to the ground.
If the twist rises above a certain value but has not exceeded the maximum twist, the system will wait for low wind conditions, and then rotate the nacelle to untwist the cables while in a “pause” condition.
If the maximum allowable twist is detected, the system will command a “stop” condition, and then drive the nacelle to zero cable twist before returning to a “run” condition.
Video: Wind Turbine Yaw System Introduction
Highland Community College as part of WindTechTV.org