Dynamic Behaviour Comparison of a 10-MW Drivetrain in a Bottom-Fixed Monopile and a Spar Floating Wind Turbines

Abstract

Up to now, very little attentions have been paid to multi-megawatt off shore wind turbine drivetrains. In order to improve the reliability of the offshore wind turbine drivetrain, a better understanding of its dynamic behaviour is a must. This study investigates the dynamic behaviour of gears and bearings of a 10-MW wind turbine drivetrain in a bottom-fixed monopile and a spar-type floating wind turbine. Environmental conditions for these two wind turbines are selected based on the long-term hindcast wind and wave data in the Northern North Sea. Identical wind speeds are used for the dynamic simulations of the two wind turbines to compare their dynamic performance. A decoupled approach is used to conduct the global and local drivetrain dynamic analysis. The global response and local drivetrain response in the two wind turbine models are compared under different load cases. Moreover, effects of global loads and nacelle motions on drivetrain dynamics are investigated individually. The results indicate that larger axial forces of drivetrain main bearings and the first stage planet carrier bearing are carried in the spar floating wind turbine than in the monopile wind turbine. In addition, global loads play the main role in drivetrain dynamic response. The present work provides a basis for drivetrain protection and optimization from floating wind turbines global analysis perspective.