Study On Dynamic Responses Of Spar Type Floating Offshore Wind Turbine With Reduced Motion Structure

The development of offshore wind power is a hot spot of the world’s new energy field.For offshore wind turbines,the basic types for different water depths are also different.The actual area of offshore wind power development in China is still mainly concentrated in the continental shelf.The seabed slopes in these sea areas are small,and most of the water depth is between 50 m and 70 m.This geographical condition limits the advantages of the floating foundation in deep water conditions.Therefore,a new type of offshore wind turbine basic type is proposed for the transitional sea area,which is of great significance for the development of China’s offshore wind power industry.In this paper,for the 70 m water depth,considering the economic and movement performance,a Spar floating wind turbine with reduced motion structure is proposed.The conceptual design of the wind turbine is introduced.The hydrodynamic performance of the floating foundation is calculated in the frequency domain by SESAM software,compared with the results of the OC3 Hywind Spar floating foundation at the same water depth.In contrast,the applicability of the Spar type floating wind turbine with reduced motion structure at the target water depth was verified.The coupled time domain dynamic analysis model of aerodynamic-hydrodynamic-mooring system is established.The numerical calculation tool is developed by Matlab.The motion response of the Spar type floating wind turbine with reduced motion structure under operating sea conditions and extreme sea conditions is studied.The power generation capacity and survivability of the wind turbine are evaluated.The influence of the second-order wave force on the motion response of the wind turbine is calculated,evaluating the complex nonlinear dynamic response characteristic.Aiming at the different structural design parameters such as center of gravity,length of mooring line,draft height and diameter of the reduced motion structure,the sensitivity analysis of hydrodynamic performance is provided,which provides a theoretical basis for further optimization of structural design.The calculation results show that for the 70 m water depth,the Spar floating wind turbine with the reduced motion structure is superior to the traditional Spar floating wind turbine and has good offshore applicability.The Spar floating wind turbine with the reduced motion structure can fully satisfy the power generation requirements under the operating sea conditions,and has good survivability under extreme sea conditions.The research work in this paper lays a theoretical foundation for the further development of Spar type floating wind turbine with reduced structure.