Study On Concept Design And Coupling Dynamic Responses Of The Articulated Offshore Wind Turbine

It is shown that the fixed foundation for offshore wind turbine is suitable for water depths below 50 meters and the floating foundation is suitable for water depths above 100 meters.Most of the coastal areas in China that are suitable for wind power development have a water depth of no more than 100 meters.For sea areas with a water depth of 50 to 100 meters,there is still a lack of a suitable foundation to support the wind turbine.In this paper,a new kind of the articulated support for offshore wind turbines is designed to support the NREL 5MW offshore wind turbine for the water depth of 75 meters.This is of great significance for solving the energy problems in China's coastal water and the southern islands and reefs.We simplify its motion into plane motion and establish its single-degree-of-freedom rigid body analysis model.The concept design of the foundation,the analysis of the inherent characteristics of the frequency domain and the coupling analysis of the time domain dynamic response were carried out.The intact stability,hydrodynamic performance and frequency domain motion characteristics are studied in the paper.For concept design,the objective function is that the average angle of pitch for the articulated support for offshore wind turbines in the load combination of the wind and wave is no more than 5°.The intact stability is studied by the statics method in consideration of the aerodynamic load of the wind turbine and the wind load of the tower.The hydrodynamic parameters are calculated through the hydrodynamic software based on the 3-D potential flow theory.And the frequency domain motion characteristics are calculated by a program of our own considering the viscous damping and the structural damping of the articulated point.The time domain coupling dynamic response of working sea conditions and extreme sea conditions is analyzed considering the combination of wind,wave and current.The aerodynamic load of the wind turbine is calculated based on the blade element momentum theory,and the wind pressure load of the tower is calculated based on the empirical formula.The program of ourselves is programmed to calculate the time domain coupling dynamic response characteristics of the wind turbine considering the changes of the instantaneous wet surface caused by the basic motion and wave height,the structural damping of the articulated point and the sea current force.The results show that the articulated offshore wind turbine's natural period of motion avoids the main periods of the ocean wave and has good inherent characteristics of motion.Also,its time domain coupling dynamic response shows that it has good motion performance,meeting the requirements of normal power generation under working sea conditions and the safety requirements of structural self-survival under extreme sea conditions.