Reliability Analysis And Optimization Of Gear Transmission System For Wind Turbines

As an essential part of renewable energy,wind power generation has been commercialized.The working environment of offshore wind turbines is complex and changeable,and it is subject to random loads such as wind and waves for a long time,which can easily cause gearboxes’ failure or even damage.As a critical component of offshore wind turbines,the gearbox has the characteristics of long downtime and high maintenance costs.Failure of any component will cause huge losses.In addition,sea traffic is affected by the weather,and the maintenance of the wind turbine is difficult.This is all reliability places high demands on it.In order to accurately predict and assess the reliability of the wind power gear transmission system,this paper establishes a dynamic model of a 5-MW offshore spar doubly-fed wind turbine,and accurately calculates the dynamic meshing force of gears through simulation,which lays the foundation for the reliability research of the gear system.Combined with the stress-strength interference theory,a time-varying reliability model of gear parts considering strength degradation was established.The equivalent normalization method was used to solve the model;the Copula function was used to consider the correlation between the failure mode and the failure of the parts.The dynamic reliability is analyzed to determine the weak links of the system,and on this basis,a reliability optimization design method is proposed.The research contents of the paper are summarized as follows:(1)Treating the stress and strength as variables,the limit state functions of gear contact fatigue failure and bending fatigue failure were established.Taking into account the random characteristics of load and the time-varying characteristics of strength,based on the stress-strength interference theory,a wind power considering residual strength degradation Dynamic reliability model of gear parts.According to the structural reliability calculation method,the equivalent normalization method is used to solve the reliability index.(2)The dynamic loads of gears are accurately calculated based on the electromechanical coupling dynamic model to fully utilize the load history and analyze time-varying reliability of gear transmission system.The rain-flow counting method is used to process the complex load-time history and convert it into a series of equivalent banner cycles stress.The statistical analysis of the rain-flow counting results is used to describe the random characteristics of the load in the reliability analysis of the gears,and the dynamic reliability of the wind power gear parts is analyzed in conjunction with the relationship between the numbers of load times of each gear.(3)The failure mode correlation and the failure correlation between gear components are studied using Copula correlation theory.The time-varying reliability of the wind power gear transmission system considering failure correlation is analyzed,and the weakest link of the system is determined.Based on this,reliability and volume are used as optimization objective functions,which are transformed into unconstrained optimization problems by interior point penalty function method,and optimization schemes are obtained based on genetic algorithms.