| The wind power industry has gone through a period of rapid development.At present,it is in the stage of frequent failure during the warranty period.The blade is not only the key component for the wind turbine to obtain wind energy,but also the key component for the unit to bear the main load.The high maintenance and replacement costs urge all parties of wind power operation and maintenance to take the effective service life of the blade as the key to cost reduction and efficiency increase.With the increase of the impeller diameter and hub height of the wind turbine,the air flow in the atmospheric boundary layer has a great impact on the wind turbine.How to excavate the non-stationary non-uniformity of the dynamic incoming flow,establish an effective wind speed model and combine it with the blade fatigue load is very important to accurately calculate the blade fatigue life value and ensure the safe and effective operation of the unit.In order to accurately calculate the evaluation value of blade fatigue life,based on the measured wind speed and direction data at the hub of wind turbine,and the progressive research idea of "non Gaussian characteristic analysis of wind","aerodynamic load analysis of blade" and "blade fatigue life analysis",the joint distribution probability model of non Gaussian wind speed and direction The variation law of dynamic incoming flow and measured aerodynamic load of wind turbine blades and the calculation model of blade life in all wind directions are systematically studied to provide technical support for blade life prediction and blade operation and maintenance management during the service period of wind farm blades.The main research work includes:(1)The non Gaussian Lévy exponential wind speed model is proposed,and the joint distribution probability model of non Gaussian wind speed and direction is established.Based on the non Gaussian nature of Lévy process,a non Gaussian Lévy exponential wind speed model is established by using the pulsation impact theory.The discrete continuous mixed joint distribution model is used to describe the variation characteristics of sixteen wind directions.The wind speed and direction joint model is established according to the measured wind speed and direction data at the wind turbine hub for many years,and the determination coefficient is used to determine the fitting of the probability density function.The example analysis shows that compared with the commonly used Gaussian wind speed Weibull distribution model,the non Gaussian Lévy exponential wind speed and direction joint probability distribution model proposed in this paper has higher fitting accuracy and can accurately show the non Gaussian characteristics of wind speed at the unit hub.The non Gaussian wind speed and direction joint distribution probability model lays a theoretical foundation for further calculation of blade life.(2)The CFD simulation method is used to simulate the simplified non Gaussian wind speed model to obtain the blade aerodynamic load,which is compared with the measured mechanical load of the blade.The CFD simulation method is used to simulate the conditions of different wind directions and wind speeds,explore the variation laws of blade aerodynamic pressure,stress and displacement,and simulate the simplified non Gaussian wind speed model to obtain the aerodynamic load of the blade.By pasting the integrated stress sensor on the blade,the real-time load change of the blade is obtained.After filtering,the real-time data is processed,stored and parallel calculated through the modular system,which is reflected in the visual intelligent wind power platform.Through the comparative analysis of examples,the variation trends of flapping moment and shimmy moment of blades obtained by CFD simulation method simulating simplified non Gaussian wind speed model and measured process are similar,which confirms the consistency and effectiveness of the results of CFD simulation method and measured blade load method.(3)The calculation method of wind turbine blade life based on all wind direction interval is proposed,and two indirect life calculation methods are compared.Based on the frequency domain method of wind speed and direction data,according to the stress damage method in all wind direction,the damage values of blade roots in different sections of broadband process are obtained by modifying the narrowband process,and the blade life calculation method in all wind direction is obtained.As the application and extension of "non Gaussian characteristic analysis of wind" and "blade aerodynamic load analysis",the traditional blade life value,measured blade life value and blade life value in all wind direction are calculated respectively through examples.The comparison shows that the traditional calculation method has overestimation risk,The results of the measured blade calculation method are close to those of the calculation method proposed in this paper.The method proposed in this paper can be combined with blade material analysis,and provides a new method with application value for the fatigue life calculation of in-service blades in wind farm. |
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