Dynamic Response And Vibration Reduction Analysis Of Floating Offshore Wind Turbine

With the development of renewable energy and increasing energy demand,the largescale floating offshore wind turbine(FOWT),which has more complex dynamic responses becomes more important to realize large-scale power generation.To reduce and avoid damaging loads and understand motion characteristics,it is important to study the motion and dynamic response characteristics of FOWT and analyze vibration reduction methods,which is of great significance to solve the problems of offshore energy and promote the development of offshore renewable energy in China.In this work,combined with hydrodynamic analysis and numerical simulation methods,the floating offshore wind turbine is systematically studied in frequency domain and time domain.The main work contents are as follows:(1)Analysis of the theoretical formulas according to the load types of FOWT.The Blade Element Momentum formula for aerodynamic load is deduced.Except the Morrison equation and three-dimensional potential flow theory,two irregular wave spectrums are given attention.(2)The hydrodynamic parameters including added mass and damping coefficient of the semi-submersible platform are analyzed in the frequency domain by using the ANSYS/AQWA software.(3)Analysis of semi-submersible FOWT in time-domain by using Open FAST based on the obtained hydrodynamic coefficients.Under the condition of initial disturbance without external load,the free decay motion is analyzed to modify the stiffness matrix.The motion and dynamic response characteristics of semi-submersible FOWT are analyzed from different conditions.(4)Investigation and verification of the vibration reduction method according to the motion responses of FOWT by using the nacelle-tower passive damping device(PTMD)and obtain the relevant parameters.According to the existing environmental conditions,the response characteristics of FOWT with passive damping structure are compared and analyzed,which shows that PTMD can well suppress the vibration of FOWT.In this work,a complete frequency and time domain analysis method of FOWT is obtained.The corresponding vibration suppression analysis is carried out.The results show that the motion responses of large-scale FOWT is more complex,and attention should be paid to the motion of FOWT in surge and pitch degree.Additionally,the passive damping device can effectively suppress the vibration response of FOWT.