Optimization Design And Fatigue Analysis Of Support Structures Of TLP Floating Offshore Wind Turbine At Deep Water

Energy is the significant material foundation to the industrial community, with the continuous improvement of industrialization standards, the large-scale use of fossil fuels has brought serious consequences. As a result, wind power, as a sort of renewable energy, has developed dramatically. Comparing with land-based wind energy, the power in deep water has natural advantages. TLP type Floating Offshore Wind Turbine (OWT) structure is a excellent carrier of developing wind power at medium depth water. It derives from Tension leg platforms in offshore oil engineering. This support structure movement frequencies across the first order wave frequency, avoids resonance between structure and the main vibration wave frequency, makes the platform structure more reasonable, and performs well in dynamics. Therefore TLP FOWTs are the best choices in deep water wind energy developing.In this paper, a mono-column TLP with 5MW turbine in medium water depth (70m-200m) is selected as an example. This paper mainly studied aspects:1.The 3D hydrodynamic finite element model is built. Hydrodynamic analysis of TLP OFWT is performed utilizing potential flow theory in order to calculate the hydrodynamic coefficients, such as wave force and the motion Response Amplitude Operators (RAO). Then, frequency domain analysis is applied to predict short term motion response for motion performance under the given environmental conditions. The result shows that the TLP OFWT has excellent hydrodynamic behavior;2.Based on modal analysis, the study on the dynamic characteristics of TLP OFWT support structure has been performed. The results of numerical examples show that the higher order frequency has a significant impact on TLP OFWT’s heave motion by harmonic analysis, transient analysis (time-history analysis);3. Based on ANSYS15.0 APDL language, applying first-order optimization method, aoptimization design program of TLP OFWT support structure (including tension legs system) is performed. In this program, the effects of the second order frequency have been focused on. The results are close to engineering standards. The method of ANSYS platform for offshore wind turbines optimization is feasible;4. Based on the linear cumulative damage theory, time-domain fatigue analysis are used to compute structures’ fatigue life of optimization results. The results show that, although the optimal design case to avoid the higher order frequency in the tension force away, the assessments of the fatigue life is not ideal, and it needs to filtrate results from other optimization sets (Feasible Sets).Studies on TLP type OFWT hydrodynamic performance computation, coupled analysis of mooring system in time domain, dynamic characteristics, optimization design program, and fatigue life are carried out in this dissertation. Meanwhile, the influence of second order sum frequency, which are sensitive to the motion performance of the TLP typeOFWT and fatigue. The research results can be served as a reference for the performance study of preliminary design.