Research On Conducted EMI Noise Diagnosis Method Based On Infomax-WT Algorithm

With the development of power electronics technology,the operating frequencies of electronic devices have been higher and higher,causing the electromagnetic interference(EMI)problems increasingly serious and some electronic devices unable to operate normally.At present,EMI research mostly focused on the modeling of noise mechanism with little concern of noise source diagnostic methods.Therefore,this thesis has carried out the research on a method of conducting EMI noise diagnosis based on Infomax-WT algorithm,which includes the following contents:(1)The working principle of the artificial power network is analyzed,and a common-mode/differential-mode conducted EMI noise model is established.The generation mechanism of conducted EMI noise in complex electronic equipment is analyzed,and a model of conducted EMI noise due to poor grounding,cable crosstalk and rising edge of switching devices is established.Finally,corresponding suppression methods are proposed for the conducted noise caused by the above different reasons.(2)The method of conducted EMI noise separation is analyzed,as well as the basic principle of Infomax algorithm,a method of conducted EMI noise separation based on Infomax algorithm is proposed with Infomax algorithm to analyze conducted EMI noise signals,and simulation experiments are performed.The simulation results show that the Infomax algorithm can achieve the separation of conducted EMI noise and achieve a good separation effect,which verifies the effectiveness of the method.(3)A diagnostic method of conducted EMI noise based on Infomax-WT algorithm is proposed.The Infomax algorithm can separate the conducted EMI noise and filter the noise source,but it can't reflect the frequency characteristics of each separated signal.To solve this problem,the Infomax-WT hybrid algorithm is proposed with the Wavelet Transform(WT)theory of time-frequency analysis.The Infomax-WT algorithm is used in the diagnosis of conducted EMI noise.Using collected conductive EMI noise samples,several independent noise signals are separated by Infomax.Each noise signal is subjected to wavelet transform to obtain the time-frequency diagram of each noise signal,and the noise source is determined according to the frequency characteristic obtained by the time-frequency chart.Finally,simulation and verification experiments are carried out.The simulation and verification results show that the method successfully identifies the noise source that causes the conducted EMI to exceed the standard and validates the effectiveness of the method.(4)The conducted EMI noise diagnosis method is applied to medical electronic equipment.The location noise source is diagnosed by Infomax-WT algorithm,and the mechanism that produces the conducted noise is analyzed.The specific inhibition methods are given.Finally,the three experimental equipments pass the standard test,which verifies the feasibility and practicality of the method.