Floating offshore wind turbines are able to access deeper waters with stronger winds, but also have more complicated dynamic behavior than fixed-bottom offshore turbines, potentially resulting in larger loads. Structural control using tuned mass dampers (TMD) is a promising method for mitigating these loads. Previous research on structural control in wind turbines has typically considered passive devices and operational conditions. In this study, the effects of a passive tuned mass damper and a semi-active tuned mass damper, located at the tower top, are analyzed and simulated for the GE Haliade 150–6MW wind turbine located on the Glosten Pelastar tension-leg platform (TLP). The system is simulated using FASTv8, the wind turbine aero-elastic wind turbine simulator developed by NREL, which includes a TMD module capable of modeling passive and semi-active devices. A pendulum-type TMD developed by ESM GmbH, which can oscillate in the fore-aft and side-side directions, is modelled with non-linear position constraints. Semi-active control is defined using an “on-off” TMD damping based on a “ground-hook” control law. Ultimate limit state (ULS) conditions with a parked rotor are simulated, for two different water depths. The results are analyzed in terms of the load reductions at the tower base, nacelle acceleration reduction, and tendon tensions for the various configurations. The impact of TMD stroke limitations and the sensitivity of the results to water depth are investigated. The results will show that structural control can reduce ULS loads in deep water configurations, but are less effective in shallow water. The dynamics of the system that cause this result will be elucidated. The results will also demonstrate that semi-active control can be an effective strategy to further reduce loads and reduce the TMD stroke.
An Investigation of Passive and Semi-Active Tuned Mass Dampers for a Tension Leg Platform Floating Offshore Wind Turbine in ULS Conditions
