Study On The Dynamic Response For Floating Foundation Of Offshore Wind Turbine

The wind resources for ocean power generation are mostly distributed in sea areas with the distance of 5～50km from coastline, whose water depth are generally over 20m. To improve ocean power output and economic benefit of offshore wind farm, it is necessary to choose floating foundation for offshore wind turbine. Therefore, it is significant to study the dynamic characertistics for floating foundation of offshore wind turbine.This paper reviews the investigation situation of floating foundations for offshore wind turbines, and puts forward important considerations for design of a floating foundation, summarizes the theories about calculation of wind, wave and current load, and introduces methods to calculate responses of a floating structure in frequency and time domain respectively. According to basic data of a 600kW wind turbine with a horizontal shaft, tower, semi-submersible foundation and mooring system are designed detailedly to make motion of the floating foundation as small as possible.The water-entrapment plates, rotor and nacelle are treated properly, precise finite element models are established using GeniE in SESAM software. In HydroD, composite model is chosen, transfer functions and response spectrums of wave load and motion of floating wind turbine system are calculated. Considering the couple between wind turbine-tower-floating foundation and mooring lines, dynamic responses of floating wind turbine system under the combination of turbulent wind, constant current and irregular wave in a 60-meter-deep sea area are calculated in DeepC. The sea state for operational condition is determined by researching dynamic motion and lines'tension, and some suggestions are given for structural optimization.The results in time domain indicate that the designed floating wind turbine system can operate safely when significant wave height is no more than 4m. The methods to design floating foundation for offshore wind turbine and calculate its dynamic responses have some referenced value for exploitation of inshore and further offshore wind resources in our country.