| The large-scale wind turbine itself has a complex overall structure,most of which are distributed in mountainous wind farms with complex terrain.It inevitably bears the effects of turbulent motion,wind shear,tower shadow effect,wake effect,and so on,furthermore,it is often operating in harsh external environments with low temperature,wind sand,and icing.Which lead to various problems,such as large system load and vibration fluctuations,high failure rates,poor reliability,difficult operation and maintenance along with high costs.In addition,according to the historical data of China’s wind turbine installed capacity growth,a large number of in-service wind turbines will reach or approach the end of their design life in the next few years.Therefore,in order to ensure the healthy and safe operation of wind turbines and improve the long-term benefits of wind farms,research and development of load monitoring and life time extension assessment technologies for large-scale wind turbines has become an urgent issue for the wind power industry.The thesis is mainly developed from the following aspects:Firstly,the current situation of the research on aerodynamic load analysis,tower load monitoring,life prediction and life time extension assessment of large-scale wind turbines is summarized and its shortcomings are analyzed.At the same time,the article introduces in detail the source of the aerodynamic load and its theoretical model and influence.Based on the principle and model description,the turbulent motion,wind shear,tower shadow effect,wake effect and other influences on wind turbine load fluctuations are analyzed.The daily and seasonal changes of turbulence intensity and wind shear are analyzed.For a more detailed study,a mathematical model for daily variation of turbulence intensity was initially established with the help of MATLAB curve fitting tools,which provided a preliminary basis for life prediction and life time extension assessment.Secondly,based on the unit parameters,wind resource data and SCADA system data of a mountain wind farm,a 1.5MW doubly-fed wind turbine simulation model is established in GH Bladed: on the one hand,the turbulence intensity obtained from the wind speed sample data is used to perform wind turbines in different seasons a comparative study of load fluctuations,on the other hand,the characteristics of load distribution along the height of the tower are analyzed based on simulation results.According to the fluctuation characteristics of wind turbine load under the seasonal variation of turbulence intensity,a targeted maintenance proposal is proposed;a tower load prediction model is established by using the genetic algorithm and particle swarm optimization algorithm to improve BP neural network algorithm,which can realize the economical and accurate monitoring of the load based on the state monitoring data of the wind turbine;The actual annual distribution parameters of wind speed based on the sample wind speed data have certain significance for improving the accuracy of life prediction and life time extension assessment.Thirdly,based on ANSYS Workbench and ANSYS n Code Design Life,the finite element static analysis and fatigue analysis of steel frame tower are performed.In this paper,a steel tower of a 1.5MW doubly-fed wind turbine in a certain wind farm is taken as an example.The tower load calculated by GH Bladed is calculated,and the static strength analysis of the steel tower is performed.Based on linear fatigue damage Cumulative criterion and Goodman condition limit correction criterion,combined with the properties of steel frame tower material Q345 D,selected the SN curve and completed the fatigue analysis.In addition,in combination with the preliminary load measurement work of the research group,a steel tower tower bolt monitoring scheme for wind turbine units is proposed,which has certain application value for tower safety monitoring and life time extension on assessment.Finally,based on the existing large-scale wind farm intelligent maintenance system of the Shanxi Wind Turbine Monitoring and Diagnostic Engineering Technology Research Center,a wind turbine life prediction and life time extension evaluation module was designed.In order to realize the life prediction of the important components of large-scale wind turbines and the evaluation of the life time extension of the whole unit,an important step was taken.Finally,the shortage and the future development were prospected. |
