Vibration suppression of floating offshore wind turbines using electromagnetic shunt tuned mass damper

This paper investigates the suppression of in-plane vibrations of a floating offshore wind turbine (FOWT) using the electromagnetic shunt tuned mass damper (EMSTMD), where the dashpot is replaced by a shunted electromagnetic (EM) transducer for improving performance and durability of the damper. A series resistive- capacitative-inductive (RCL) network is designed as the supplemental shunt for the EM transducer, which results in an additional resonance for performance improvement. A 17-degree-of-freedom (17-DOF) aero-hydro-servo-elastic model is established for the FOWT, which is used for performance evaluation of the EMSTMD in the time domain. A reduced-order 6-DOF model is then developed for the FOWT in-plane vibrations with EMSTMD mounted, accounting for rotor mass moment of inertia, stiffness from buoyancy and mooring lines, as well as hydrodynamic added mass. This model facilitates an efficient frequency-domain optimization procedure for the EMSTMD, taking into account uncertainties in the environmental conditions. The performance of the optimized EMSTMD is compared with that of the classic TMD in both frequency and time domains. It is shown that both EMSTMD and TMD effectively reduce tower side-side vibrations of FOWT, and also have lightly positive effect on the spar roll and blade edgewise vibrations. EMSTMD consistently outperforms TMD for all environmental conditions, at the cost of slightly increased absorber stroke.