Research On Fault Diagnosis Of Wind Turbine Planetary Gearbox Based On Speed Estimation

In practice,wind turbines are mostly operated under variable speed conditions,which will lead to the problem of spectral ambiguity of gearbox fault characteristics,and the gearbox fault diagnosis method based on constant speed is no longer applicable to variable speed conditions.The key for variable speed gearbox fault diagnosis is to obtain the speed-related information,and the usual method to obtain the speed is to use tachometer,but this method has the limitations of insufficient equipment installation space and high cost,so it is meaningful to obtain the instantaneous frequency from the vibration signal itself and then obtain the speed information for wind turbine gearbox fault diagnosis.This paper presents a systematic analysis and diagnosis of wind turbine gearbox faults based on SEV instantaneous frequency estimation,and the method mentioned in the paper is verified by simulation and experiment.A new method is proposed for the fault diagnosis of variable speed wind turbine gearboxes without tachometer,which makes a contribution to the application and development of fault diagnosis theory.In this paper,the planetary gearbox of wind turbine at variable speed is studied in the following aspects.The structural characteristics of wind turbine gearboxes and the common failure forms of internal gears and bearings are introduced,the failure characteristics under different failure forms are analyzed,and the failure signal models of gears and bearings under different failure characteristics are introduced to provide a failure signal simulation model for later simulation analysis.In order to carry out the fault diagnosis of variable speed wind turbine gearboxes without tachometer,the local energy maxima method and the instantaneous frequency estimation method based on the combination of synchronous extraction and Vold-Kalman filter are proposed.The instantaneous frequency estimation ability of these two methods and the peak search method under the background noise with different signal-to-noise ratios are compared and analyzed to provide a theoretical basis for fault diagnosis of tachometer-free gearboxes.For the problem of planetary gear failure in variable speed wind turbine,the order analysis method and the structure of wind turbine gearbox rotating test bench are introduced.The analysis is carried out by simulation and experiment to obtain the fault order spectrum of planetary gearbox at variable speed,and compare the accuracy of local energy maxima method and instantaneous frequency estimation method based on the combination of synchronous extraction and Vold-Kalman filter,as well as the fault diagnosis capability of order analysis based on the two methods in wind turbine planetary gearbox fault diagnosis.According to the characteristics of the gearbox high-speed end bearing prone to failure,the effect of speed change on the vibration signal is analyzed,and a resonance demodulation method based on angle domain autocorrelation spectral kurtosis is proposed.Compared with the angle domain fast spectral kurtosis resonance demodulation method,the simulation and experimental data are analyzed to get the kurtosis spectrum and square envelope spectrum of fault signal,which verify the bandwidth selection effect and signal demodulation ability of the proposed method.