A real-time hybrid simulation framework for floating offshore wind turbines

Abstract

Offshore wind farms are experiencing rapid growth globally where floating offshore wind turbines (FOWTs) have been attracting increasing research and industry investment. To achieve secure application, it is essential to develop numerical models and conduct laboratory testing to develop an in-depth understanding of the complex structural behavior of FOWTs under combined wind-wave loading. However, model testing of FOWTs is complicated by the Reynolds-Froude scaling incompatibilities. This research proposes a real-time hybrid simulation (RTHS) framework to study the structural performance of FOWTs under wind-wave loading. In the framework, the blades (nacelle) and tower are numerically modeled, and the floating platform is tested in real-time via an actuation system in a laboratory. The numerical and physical substructures communicate at the tower-floater interface. The National Renewable Energy Lab 5 MW spar-type FOWT on a scale of 1:50 is simulated to evaluate the feasibility of the proposed framework. Errors caused by delays and noises are quantified through sensitivity analyses. Results show that the delays in the sensors and actuators influence the performance of the RTHS framework more significantly than the noises. Overall, the response relative errors in the RTHS framework are small and tolerable under delays, noises, and representative wind-wave conditions. The proposed framework and sensitivity analyses presented in this study provide important information for future implementation and further development of the RTHS technology for similar marine structures.