Vibration suppression for monopile and spar-buoy offshore wind turbines using the structure-immittance approach

Oshore wind turbines have the potential to capture the high-quality wind resource. However the signicant wind and wave excitations may result in excessive vibrations and decreased reliability. To reduce vibrations, passive structural control devices, such as the tuned mass damper (TMD), have been used. To further enhance the vibration suppression capability, inerter-based absorbers (IBAs) have been studied using the structure-based approach, i.e. proposing specic stiness-damping-inertance elements layouts for investi
gation. Such an approach has a critical limitation of being only able to cover specic IBA layouts, leaving numerous benecial congurations not identied. This paper adopts the newly introduced structure-immittance approach, which is able to cover all network lay out possibilities with a predetermined number of elements. Linear monopile and spar-buoy turbine models are rst established for optimisation. Results show that the performance improvements can be up to 6.5% and 7.3% with 4 and 6 elements, respectively, compared to the TMD. Moreover, a complete set of benecial IBA layouts with explicit element types and numbers have been obtained, which is essential for next step real-life applications. In order to verify the eectiveness of the identied absorbers with OpenFAST, an approach has been established to integrate any IBA transfer functions. It has been shown that the performance benets preserve under both the Fatigue Limit State (FLS) and the Ultimate Limit State (ULS). Furthermore, results show that the mass component of the optimum IBAs can be reduced by up to 25.1% (7486kg) to achieve the same performance as the TMD.