Study On Harmonic Distribution Characteristics And Probability Model For High Speed Railway Traction Load

With the development of Chinese high-speed railway and the existing line expansion,electric railway power quality problem has been receiving much concern.Because the high speed railway traction load harmonic distribution directly affects the quality of power supply,the traction load harmonic probability distribution model and forecasting method are the important foundation of power quality prediction,assessment and comprehensive treatment.In this paper,according to the characteristics of high speed railway traction load harmonic random fluctuations,based on the measured data of high speed railway traction load,on the basis of existing achievements,using probability theory and mathematical statistics knowledge,according to different boundary conditions on the basis of the testing data on a large amount of traction substation classification analysis,harmonic current probability model is established,and the new construction on electric railway power quality is predicted,the effect of traction load harmonic penetration is researched when new high speed railway connecting to the electricity grid.In this paper,the main content is as follows:First of all,based on the existing of the multiple high-speed lines measured data,considering the correlation between the harmonic current containing rate and traction load power,part of the substation harmonic measurement data as example,using nonparametric kernel density estimation method for every harmonic current containing rate,the probability density of piecewise is fitted in different power range,the actual calculation is described in detail in the choice of bandwidth,which are compared with the beta distribution fitting methods with determine coefficient as the check to best fitting indicator.Second,this paper put forward the prediction method of high speed railway traction load harmonic based on the confidence interval.Based on distribution characteristics of traction load,probability distribution characteristics of both line traction load classification and characteristic parameters are managed,selecting the typical characteristic parameters as boundary conditions,high speed railway traction load harmonic distribution are predicted.Meanwhile,comparing with lines of measured data and simulation data,the validity of harmonic prediction method is proved.Finally,according to the loads' coincidence factors put forward in technical document(GB/Z 17625.4-2000),the high-speed railway traction load coincidence factors are computed.Based on the predicted data of new line traction load harmonic,when new high speed railway connecting to the electricity grid,the effect of traction load harmonic penetration is researched with NeHarml.0 simulation platform.According to the bearing harmonic capacity abundance of electric equipment of the medium and low voltage electrical system,the traction load harmonic limits can be computed,which lead to the reasonable assessment of safety of power grid traction effected by load harmonic.