Distributed real-time hybrid simulation method for dynamic response evaluation of floating wind turbines

Limited land and near coast spaces led to the development of floating wind turbine (FWT) farms in unlimited space of deep water with steady winds. Experimental evaluation of dynamic responses of FWT is essential to ensure its safe operation. However, due to laboratory limitations and scaling issues, realistic FWT responses are difficult to be replicated on scaled-down test specimens. To facilitate larger-scale testing of FWT and apply realistic wind and wave loads, distributed real-time hybrid simulation (dRTHS) method is proposed which combines the testing of FWT substructures at geographically distributed laboratories using wind tunnels and wave tanks. In this research, dRTHS experimental method for FWT is developed and its feasibility is verified through a series of virtual dRTHS (vdRTHS) and proof-of-the-concept partial dRTHS tests. The equation of motion of a prototype FWT structure under coupled aerodynamic and hydrodynamic loads was partitioned to represent the wind turbine tower and platform substructures, based on which substructural formulation was derived. During the vdRTHS, two distributed real-time controllers were used to simulate the physical testing of the two substructures tested in the wind tunnel and water tank, respectively, with interfacing data being transferred in real-time through a network. FWT responses from vdRTHS match well with those obtained from numerical simulations of the whole FWT model and the substructured models, demonstrating that the feasibility of the proposed dRTHS method. In addition, the substructuring approach, the vdRTHS testing platform, and the method to overcome network communication delay are effective in the vdRTHS resulting in reliable FWT dynamic responses under coupled loading conditions. Furthermore, the proposed dRTHS concept was verified through a partial distributed physical tests during which the wind turbine substructure was tested physically, while the platform substructure and the hydrodynamic loads were simulated numerically.