Reliability Analysis And Maintenance Optimization Of Wind Turbine Under Epistemic Uncertainty

Energy is closely related to human beings.As the energy shortage and environment crisis intensify,wind energy has gained significant attention due to its safety and cleanness,and the related wind energy technology has developed fast in past decades.With the increase of the capacity of wind turbine generators,wind turbine generator systems have become more complicated,particularly for the megawatt-scale wind turbine generator systems.For the megawatt-scale wind turbine generator systems,more attention should be paid to their reliability assessment due to the following two reasons:(1)As the wind turbine is operating outdoor and the lifetime of wind turbines is greater than 20 years.To reduce losses caused by failures,it is of great significance to ensure long-term stable and reliable operation of the wind turbine under various weather conditions;(2)Due to the high requirement of the working environment for the wind turbines,most of the wind turbines are located in remote areas such as plateaus or seaside.Meanwhile,the main body of the wind turbine is set up at a high altitude when operating.Therefore,the maintenance activities for the wind turbine are challenging and costly.This thesis devote to the reliability analysis and maintenance optimization of the2.5MW wind turbine designed by Taiyuan Heavy Machinery Group Co.,Ltd.The major contributions of this thesis are as follows:(1)The main drive system of the megawatt-scale wind turbine generator system is analyzed based on FMECA method.FMECA method is one of the most commonly used reliability analysis methods.The main drive system is the most prone to failure part in the whole megawatt-scale wind turbine generator system.The structure and function of the main drive system are analyzed,and then,the system definition,hierarchical division,and fault analysis of the main drive system is done based on the national military standard GJB/Z1391-2006.On this basis,the criticality analysis is carried out by utilizing the risk priority number,and the FMECA form is completed(2)The availability of the whole wind turbine generator system is evaluated based on the fuzzy general generating function method.For the complex equipment such as the megawatt-scale wind turbine generator system,the traditional binary-state system model is no longer applicable.According to the actual operation of the wind turbine,the reliability modeling of wind turbine based on multi-state reliability theory is done.The universal generating function method is used to evaluate the reliability of the model,whereas the performance levels and state probability distribution of each component are treated as triangular fuzzy numbers due to epistemic uncertainty.Tthe fuzzy availability of the system under the fuzzy system demand is caculated.(3)A maintenance optimization method is proposed for the wind turbine under epistemic uncertainty.In the proposed method,a selective maintenance model is established for the wind turbine generator system,which is viewed as a multi-state system.The Markov decision process is proposed to resolve the selective maintenance problem.By combining the Markov decision process with the fuzzy theory,the reward and the state distribution of the system are represented as triangular fuzzy numbers to quantify the epistemic uncertainty.Finally,based on this method,the maintenance decision of the wind turbine generator system can be optimized.