Hydraulic Yaw System

As wind turbines increase in size, combined with increased lifetime demands, new methods for load reduction needs to be examined. One method is to make the yaw system of the turbine soft/flexible and hereby dampen the loads to the system, which is the focus of the current paper. By utilizing the HAWC2 aeroelastic code and an extended model of the NREL 5MW turbine combined with a simplified linear model of the turbine, the parameters of the soft yaw system are optimized to reduce loading in critical components.
Results shows that a significant reduction in fatigue and extreme loads to the yaw system and rotor shaft when
utilizing the soft yaw drive concept compared to the original stiff yaw system.
The physical demands of the hydraulic yaw system are furthermore examined for a life time of 20 years. Based
on the extrapolated loads, the duty cycles show that it is possible to construct a hydraulic soft yaw system, which is able to reduce the loads on the wind turbine significantly.
A full scale hydraulic yaw test rig is available for experiments and tests. The test rig is presented as well as the system schematics of the hydraulic yaw system.