Research On Power Harmonic Detection Technology Based On Hilbert-Huang Transform

In recent years,with the gradual improvement of the power system,more and more non-linear electronic devices are used in the power system,resulting in increasing harmonic problems,which is harmful to the safety of users and the normal operation of equipment.The research of harmonic detection method is the premise of harmonic control.According to the detection result,it is of great practical significance to take appropriate harmonic suppression measures.This paper focuses on five aspects:1.This paper studies the basic theory of harmonics,constructs a harmonic analysis framework,and discusses the advantages and disadvantages of several harmonic detection methods commonly used at home and abroad.To the deficiency of traditional harmonic analysis methods,Hilbert-Huang(HHT)algorithm is used for harmonic detection,and the development history of HHT power system harmonic detection is summarized in recent years.2.This paper introduces the advantages of HHT algorithm with adaptive decomposition and the basic theory of HHT,and describes the empirical mode decomposition(EMD)and Hilbert transform(HT)in detail.This paper discusses the theoretical immaturity,endpoint effects,false components,and termination criteria of HHT.3.Research on the end effect problem of HHT harmonic detection.The four extreme point effect suppression methods of extreme point extension,mirror extension,parallel extension and slope re-optimization(RO-SBM)extension are used for harmonic signal processing,and the comparison experiment of the four methods shows: RO-SBM can effectively suppress the end effect of HHT harmonic signal processing.Furthermore,combine RO-SBM extension with HHT harmonic detection(RO-SBM-HHT),which can effectively suppress the end effect of harmonic signals.4.Research on the problem of modal aliasing and false components in HHT harmonic detection.The reason for modal aliasing in HHT harmonic signal processing is that there is a signal within 2 times the frequency.For this reason,the use of high and low pass filter technology can effectively solve the problem of modal aliasing.However,the selection of different types of filters will affect the suppression of modal aliasing.By analyzing the application of Butterworth type,Chebyshev type 1,Chebyshev type 2,elliptic high-pass and low-pass filters in harmonic detection,it is concluded that Chebyshev type 1 high and low pass filters are more effective in suppressing modal aliasing.For the false component problem,the energy ratio method is used to measure the energy ratio between the IMF component and the original signal,and the false component can be identified and removed according to the energyratio.Based on the RO-SBM-HHT harmonic detection algorithm,an adaptive RO-SBM-HHT harmonic detection algorithm is proposed.The algorithm can identify the magnitude of the instantaneous frequency drop of the IMF component,and adaptively select the corresponding method to suppress the endpoint effect and modal aliasing problems,and eliminate the false component in harmonic detection.Therefore,the algorithm improves the detection accuracy of harmonic parameters5.The adaptive RO-SBM-HHT harmonic detection algorithm HHT algorithm is applied to harmonic measurement and analysis.MATLAB is used to simulate the smooth and fluctuating harmonic signals in the distribution network,and compared with FFT or wavelet transform.The results show that the algorithm in this paper can effectively decompose the harmonic signal,and can effectively suppress the end effect and modal aliasing phenomenon,and remove the false components.The algorithm’s harmonic detection accuracy and fluctuation start and end time parameters are superior to other algorithms.The analysis of simulation harmonic experiment data shows that the amplitude and frequency measurement of the algorithm in this paper are within the error range,the detection accuracy is better than the FFT algorithm,and it has certain practical application.