Development of a Mathematical Control-Oriented Model for Floating Offshore Wind Turbines

Wind turbines are highly efficient energy converters that exploit locally available renewable resources across many regions. In modern floating offshore wind turbines (FOWTs), strong aerodynamic and hydrodynamic loads give rise to nonlinear and tightly coupled dynamics, which typically require dedicated—and computationally demanding—simulation tools for analysis and control design. This work introduces a simplified, control-oriented mathematical model of a FOWT, derived directly from fundamental force and torque balances and explicitly incorporating the gyroscopic effect, which is often neglected in onshore wind turbines due to its comparatively lower significance. Model parameters are identified for the NREL 5-MW reference turbine using autoregressive models with exogenous input (ARX) techniques. The proposed model is validated against the standard NREL OpenFAST simulation framework. Its utility is further demonstrated by designing a classical control system based on the simplified model and applying it to a high-fidelity nonlinear FOWT simulation, yielding satisfactory performance. The main advantages of the model are: (a) its compact parameter set enables computationally efficient simulations; (b) its feedback structure is based on relative forces, making it applicable under a broader range of disturbances than conventional input–output models; (c) its simplicity facilitates the identification of fundamental behaviors and rapid assessment of dynamic couplings; and (d) its structure is easily modifiable, allowing redesign of components or targeted alteration of the system dynamics through control actions. Overall, the model remains fully explainable, preserving a clear link to the underlying physical principles.