Research On Propagation Characteristics Of Harmonic In Transmission Line

Due to wide application of nonlinear electrical equipment,there are more and more harmonic in electric transmission line,which damages safe operation of power transmission system.Therefore,the study of harmonic propagation characteristics in transmission lines can provide theoretical support for harmonic control.Aiming at the problem that different harmonics have different influence on transmission line parameters.According to the Carson integration and earth loop correction theory,the frequency parameter matrix of transmission line is obtained.As the grounding mode of overhead ground wire will affect frequency dependent parameters of transmission line,this paper studies the method of eliminating the ground line under three grounding modes,calculating the frequency parameter matrix after eliminating the ground lines,verified by programming in MATLAB.Considering the propagation characteristics of harmonics in transmission lines,it is necessary to establish an appropriate harmonic transmission line model;Therefore,this paper made a deep research on the line Bergeron model and JMarti model,the equivalent method,time domain and complex frequency domain transform,simulation and other aspects of the comparative analysis of two kinds of line model.The JMarti model is considered as the line harmonic model to study the harmonic propagation characteristics in transmission lines more accurately.The transmission characteristics of harmonics in transmission lines are analyzed by studying the harmonic transfer coefficient.Under the two conditions of no-load and load,the harmonic transfer coefficient is derived theoretically and verified by simulation.Considering the factors influencing the harmonic transfer coefficient,including line length,harmonic frequency,load types etc.Through establishing the simulation of the harmonic line model,the influence of each factor is obtained.According to the actual structure parameters of South Shaanxi transmission network,the transmission system is established by ATP simulation software.The over limit problem of harmonic current and harmonic voltage of each node in the transmission system are studied,which provides a theoretical basis for the overall harmonic control of the transmission network in the south of Shaanxi.