Fault Diagnosis Method For Rolling Bearing Of Wind Turbine Under Variable Operating Conditions

Wind power,as the third main power supply,has broad space for development.As the new units are constantly in operation,the old units gradually enter the period of multi-faults.If the fault cannot be dealt with in time,it will affect the safe and economic operation of the wind turbines.Therefore,it is of great significance to study the condition monitoring and fault diagnosis of wind turbines to prevent the occurrence of major accidents and reduce the cost of operation and maintenance.In this paper,the rolling bearings with higher failure rate are analyzed.An in-depth study of the fault feature extraction and diagnosis of rolling bearing is to be conducted under the condition of constant speed and complicated working condition.The main contents are as follows:(1)The wind turbine rolling bearing is used to be the main research object in this paper.In order to provide theoretical basis for fault diagnosis of rolling bearing,composition structure,position distribution,fault mechanism,fault type and fault characteristic frequency are analyzed.And by analysis,acquiring effective fault diagnosis methods in time domain,frequency domain and time-frequency domain under different operating conditions.(2)Research on fault feature extraction and diagnosis of rolling bearings for wind turbine under constant speed conditions.The methods of wavelet packet decomposition(WPD)and variational mode decomposition(VMD)are used to begin diagnostic analysis of laboratory and field vibration data.When wavelet packet is used to decompose the fault signal,the Shannon information entropy method is chosen as the information cost function.And the best decomposition scale of wavelet packet is selected through comparison test.To select the four aspects of decomposition characteristics,diagnostic effectiveness,flexibility of use,and running time as comparison objects,this paper comprehensively compares and analyzes WPD and VMD.(3)Research on fault diagnosis of rolling bearings under variable speed and variable load conditions.Based on the reversed sequence squared envelope spectrum(RE-SES)of VMD,a method of rolling bearings fault diagnosis under variable speed is proposed in this paper.And it contrasts with an algorithm of COT-VMD,which combines the technology of computed order tracking(COT)with the algorithm of VMD.In this paper,the principle and implementation process of RE-SES and COT-VMD based on VMD filtering are explained clearly.The rolling bearings running condition under variable speed and load are simulated by test stand,and there is a research on the rolling bearings diagnosis of normal state,inner ring fault,outer ring fault,rolling body fault and compound fault.Based on VMD filtering,the three aspects of process,diagnostic effect,and runtime,which belong to RE-SES,are compared with the same three aspects of COT-VMD,and analyzed.Finally,the main conclusions of this paper are presented,and the direction and content of further research are prospected.