State of the art-hydraulic yaw systems for wind turbines

This paper addresses the yawing systems of Horizontal Axis Wind Turbines (HAWT’s). HAWT’s represents close to all of the commercial large wind turbines sold today and must be considered state-of-the art within wind turbine technology.

Two choices exists when considering components for the active yaw system of a HAWT, electro-mechanical or hydraulic components. In the first generation of larger WT’s hydraulic yaw systems outnumbered the electrical, but in the more recent years there has been a clear shift toward electrical drives, where the yaw drive consist of multiple induction motors each mounted with a reduction gear. This paper presents state-of-the art within; hydraulic yaw system design and control of yaw systems in general. Primary focus on the advantages and disadvantages of using a hydraulic system for controlling the yaw of a wind turbine with a soft yaw concept.