Research On Harmonic Recognition And Extraction Based On EMC Test

With the large-scale use of high-frequency and high-speed devices such as high-power non-linear devices and power conversion in electronic devices,the performance and integration of devices and systems are continuously improved,but increasingly serious harmonic interference is also generated between electronic devices.The electromagnetic compatibility of the system is degraded.In order to solve such EMC problems,EMC testing of the system or equipment is required,and based on the test results,harmonic characteristics in the current electromagnetic environment are extracted and identified,and then electromagnetic compatibility maintenance is performed.In order to solve such electromagnetic compatibility problems,the characteristics of harmonic interference sources of the system or equipment need to be studied,and then the frequency and amplitude of the harmonic signals in the current electromagnetic environment are extracted and identified based on the test results.However,the harmonic signal in electromagnetic compatibility test is a kind of blind source signal based only on frequency domain characteristics,and there may be multiple harmonic interference sources in the same frequency band of EMC test data,so the test data composition is complex,which leads to fault diagnosis.The difficulty of rectification and reform is so great that testers need to constantly test and verify the suspected sources of interference,which takes a lot of time and manpower.Therefore,in order to improve the test efficiency and effectively use the harmonic characteristics contained in the electromagnetic compatibility test data of the system or equipment,the testers are required to study the harmonic data laws in the EMC measured data and the characteristics of typical harmonic interference sources in the electronic equipment.How to apply the research results to harmonic recognition and extraction of equipment or system has become an urgent problem.In this paper,according to the electromagnetic compatibility test and the frequency domain data characteristics of harmonics,and the analysis of the harmonic characteristics of typical electromagnetic interference sources,the harmonic identification and feature extraction schemes in electromagnetic compatibility testing are studied.Then a new method of harmonic feature extraction based on distance matrix was designed.Finally,the MFC framework was used to implement the electromagnetic compatibility harmonic feature extraction software.First of all,this article introduces the definition of harmonics,and summarizes the characteristics of harmonic signals in the frequency domain based on the Fourier transform process of different kinds of ideal signals.Then,in the context of electromagnetic compatibility test items and test methods,this paper points out the difficulties in the representation of harmonic signals in the EMC measured data and the difficulties in extracting harmonics.Then,this paper classifies the sources of harmonic interference according to the generation method and influence mechanism of interference sources in electromagnetic compatibility.Next,the typical harmonic interference sources are selected in this paper.Their working principles and the mechanism of harmonic generation are analyzed in detail,and the results of the actual electromagnetic compatibility test are used to verify these analysis conclusions.Finally,based on the analysis of these harmonic interference sources,this paper summarizes the commonality of electromagnetic harmonic interference sources,and provides the basis for the identification and extraction of the EMC harmonic source harmonic feature extraction and its application value.Finally,this article designed a harmonic identification and feature extraction scheme for electromagnetic compatibility testing.Then,according to the characteristics of the actual test data,a series of harmonic extraction algorithms such as data preprocessing method,noise threshold processing method and harmonic signal feature extraction method are designed and implemented by software.Then the radiated emission test results of a certain signal source were used to verify the example and the effectiveness of the software was demonstrated.