Research On Model-based Wind Turbine Thermal Characteristics And Fault Diagnosis

Nowadays,large commercial wind turbines and wind farms are usually equipped with SCADA systems to record the unit operation data and alarm information.But the application of SCADA data for the on-line monitoring and fault diagnosis of wind turbines is still a key problem waiting for solution.Therefore,the study of wind turbine thermal characteristics and on-line fault diagnosis are carried out in this paper.For the disadvantages of common data-based methods,this research presents a new model-based method of wind turbine fault diagnosis,which provides a feasible and effective technical mean for the wind turbine thermal analysis and development of the on-line monitoring and fault diagnosis system.The main research contents are as follows:(1)For the nonlinear dynamic characteristics of the double-fed induction wind turbine,the mathematical models of wind turbine components are derived based on the physical structure and principle of a wind turbine.The dynamic responses of a wind turbine under different wind speed and control strategies are simulated by the wind turbine model with Matlab/Simulink.The simulation results demonstrate that the wind turbine model established in this paper shows the nonlinear characteristics of double-fed induction wind turbine and the relationship between its variables.(2)The model-based fault diagnosis method of wind turbines based on the thermal characteristics is proposed from the view of energy conversion.With study of the power dissipation and heat transfer in the wind turbine gearbox and generator,thermal models of the gearbox and the generator are established respectively based on lumped parameter method and equivalent thermal network method.The nonlinear characteristics of gearbox and generator parameters under different wind speeds are studied by combining the wind turbine model with the thermal models.The results show that gearbox transmission efficiency,lubricating oil temperature and stator winding temperature change with the working condition.The simulation examples are given to illustrate the rationality of the proposed model.(3)For the problem of nonlinear state estimation of a wind turbine,comparison results of the estimation accuracy between EKF and UKF algorithm show that UKF algorithm avoids the error caused by model linearization and has higher accuracy,faster convergence and stronger robustness,which is less affected by the measurement step.A fault diagnosis approach based on UKF is developed to estimate the reference values of wind turbine monitoring variables.(4)For the similar changes of certain parameters caused by different faults in a wind turbine,four different failure modes are introduced in wind turbines by modifying the model parameters.The influences of different fault mechanisms on the nonlinear characteristics of a wind turbine are studied.Temperatures are adopted as main monitoring quantities to identify different faults on the basis of model-based method.Simulation results show the different capabilities of model-based method to different failure modes.There are differences in residuals between actual and referential values,which makes it possible to detect the fault with the residual behavior.On this basis,the sensitivity and applicability of model-based method to different fault mechanism are studied.The simulation examples are given to illustrate the effectiveness of the proposed model-based method.(5)The application of low frequency SCADA data in fault diagnosis of the wind turbine is studied.The reference values of lubricating oil temperature and stator winding temperature are obtained by the presented model-based method.By comparing reference values with the actual SCADA data,the gearbox fault and generator cooling system fault are identified referring to the related maintenance information.In addition,there is a response to the potential risk a period of time before the shutdown caused by gearbox faults.The processes and results of comparison with SCADA data illustrate the validity and effectiveness of the proposed model.The researches in this paper provide theoretical bases and technical means for the study of wind turbine operation and thermal characteristics,reliability design,development and application of fault diagnosis system.