Extreme And Fatigue Loads Of Wind Turbines

The design of the turbine structure needs to meet the requirements of ultimate limit state analysis,including analysis of ultimate strength and analysis of fatigue failure.The research in this paper focuses on the general algorithm of extreme load prediction and fatigue load analysis.The Classical Extreme Value Theory is introduced to conduct a more in-depth exploration on the Integration Method proposed by IEC standard.Combining respective advantages of Block method and POT method,an extreme point extraction method owning both extraction efficiency and independence advantages is proposed.The Generalized Extreme Value distribution is used to fit the extraction points and the linear moment method to estimate the distribution parameters.The QQ plot is drawn to test the fitting distribution,which solves the problem of fitting accuracy encountered in similar studies and reduces the high quantile load fitting error.The algorithm is applied to calculating the WP_Baseline wind turbine extreme load,and finally the exceedance probability curve closer to the "real data" is obtained.The First-Order Reliability Method is used to study the calculation of the extreme load of offshore wind turbines.Innovatively combining IFORM's two-dimensional formal Environmental Contour Method with the one-dimensional optimization method Dichotomy to form a more efficient search algorithm for the OC3 Hywind wind turbine's extreme load calculation.Finally,it is compared with the Integration Method to verify that the search algorithm has less computational cost and high reliability.According to relevant requirements put forward by the IEC standard,the general method for calculating the fatigue load of wind turbines is studied.Using the large volume of data acquired during the study of the extreme load,MLife is used to extract load cycle and the minimum cycle amplitude is set for filtering.Then,the short-term load spectrum is calculated by counting method and distribution method.Finally,the integrating range of short-term load spectrum is extended to the whole operation life,and the long-term load spectrum of each load object is obtained.