Dynamic Characteristics Analysis Of Braceless Semi-submersible Offshore Wind Turbine Under The Combined Wind And Wave Conditions

China has a vast coastline and abundant offshore wind energy resources,which is suitable for the development of offshore wind power.It can reduce the occupation of land resources,improve the energy industrial structure,and ease the contradiction of energy supply,which plays a very important role in the optimization of China's energy industrial structure.For an offshore wind turbine,its motion response and mooring line tension are also different under different wind loads,waves,currents and other environmental loads.In addition,under the action of extreme coherent gusts,the viability of the wind turbine is further tested.In this paper,based on Braceless semi-submersible floating offshore wind turbine and considering different working water depth conditions,the sweep analysis of the rated working condition and extreme working condition of the floating offshore wind turbine under the combined action of wind waves was carried out,and the dynamic characteristics of the wind turbine under the action of extreme coherent gust were studied.The main contents of this paper are given as follows:(1)Screen analysis of Braceless semi-submersible floating offshore wind turbine with a depth of 100 m.Platform motion response model is established based on ANSYS-AQWA,use AQWA software,the hydrodynamic load with potential flow theory and Morrison equation,the wind load with Blade element theory,respectively under the rated conditions and extreme conditions,wind current load combination of different angle computing platform,respectively,six degrees of freedom movement response and time domain response mooring line tension.(2)The working conditions corresponding to the maximum occurrence of the mooring line and the maximum occurrence of the motion response in(1)were set as the typical working conditions.For the water depths of 150 m and 200 m,the motion response of the platform with six degrees of freedom and the time-domain response of the mooring line tension were calculated respectively,and the safety coefficient was compared with the specification.Mooring lines appear in(1)the maximum and the motion response appears corresponds to the maximum operating mode is set to typical working conditions,and 200 m water depth of 150 m depth of Braceless semi-submersible offshore wind turbine respectively computing platform six degrees of freedom movement response and time domain response mooring line tension,to extract the maximum tension of time domain and the corresponding operating mode,safety coefficient calculation,and comparing with the safety factor of the rules and regulations of ABS,evaluate the mooring system safety performance.(3)Braceless semi-submersible offshore wind turbine in extreme coherent wind under the action of the dynamic characteristics analysis,from the rated wind speed of the wind turbine to 20 m/s wind speed change process is not long extreme coherent wind at the same time,explore the extreme length of action coherent wind effects on tension of mooring system and the platform motion response,evaluate the mooring system safety and puts forward suggestions on mooring system design.