Detection Of Harmonic Source And Evaluation Of Harmonic Emission Level In Distribution Network

With the wide use of power electronic devices,the harmonic pollution of the power system is becoming more and more serious,and the hope of "green" electric energy is becoming more and more intense.The accurate detection of harmonic sources in distribution network plays a positive role in harmonic harnessing and power quality improvement.And the implementation of the "reward and punishment system"is more dependent on the good evaluation of the level of harmonic emission.In this paper,firstly,the existing harmonic source detection methods in distribution network are classified and introduced.Further,the harmonic emission level evaluation technology is classified and analyzed,and the advantages and disadvantages of all kinds of methods are summarized.Based on the equivalent circuit method,the harmonic detection method of reactive power,according to the different definitions of reactive power under non sinusoidal conditions,and the relation and differences in regularity in the special system environment,so as to realize the detection of the main harmonic sources.And through the observation of the simulation results,the influence of the shunt capacitor on the detection of harmonic source is further studied.Secondly,the independent component analysis algorithm is applied to the detection of harmonic source in the distribution network,which is a method based on the harmonic state estimation.This paper introduces the basic principle of the independent component analysis algorithm,analyzes its common target function and optimization algorithm,and expounds the shortcomings of the algorithm and makes improvements.A mathematical model of harmonic source detection is set up.The harmonic voltage is measured and the improved FastICA algorithm based on the negative entropy is used to estimate the harmonic source current.Combining the mutual information theory,the detection of the location of the harmonic source is finally realized.Finally,by analyzing the principle of partial least squares,the limitation of its application is improved,and the evaluation method of harmonic emission level based on orthogonal partial least squares is proposed.The proposed method is used to estimate the equivalent harmonic impedance of the system and calculate the harmonic emission level of the system.The results show that the method can effectively estimate the harmonic emission level,and the accuracy is higher than the traditional method,and the stability is better.