Torsional Vibration Characteristics Analysis of Floating Offshore Wind Turbines with Virtual Synchronous Generator Control

This paper investigates the torsional vibration characteristics of floating offshore wind turbines (FOWTs) under the influence of both wind-wave disturbances and grid interactions, particularly when controlled by a virtual synchronous generator (VSG). A simplified planar structural model of a 5-MW semi-submersible FOWT, based on the NREL reference turbine, is developed to capture the effects of environmental excitations. A grid-connected model of a permanent magnet synchronous generator (PMSG) wind turbine with VSG control is established to describe the interaction between structural dynamics and converter-based control. Simulation results in MATLAB/Simulink reveal that platform-induced motion leads to instability in the reference rotor speed generated by the maximum power point tracking (MPPT) controller, causing mismatch between mechanical and electromagnetic torque. This dynamic mismatch can excite torsional oscillations through electromechanical coupling, potentially triggering resonance. The findings highlight the importance of integrated modeling of structural and control systems, and the future work should focus on developing effective damping strategies.