Power Flow Analysis Of Traction Network Based On Load Characteristics

In recent years,with the rapid development of the electrified railway in our country,the train running speed,running density and running power are all increasing,which brings convenience to people's life at the same time,it also brings a series of power quality problems to the traction power supply system,such as negative sequence,harmonic,voltage fluctuation and so on.Traction network is one of the main components of the traction power supply system,and it has an important impact on the safe and stable operation of the train.Therefore,it is imperative to establish the simulation model of the locomotive-traction network and analyze the power flow of the traction network.Taking the traction network of the electrified railway as the research object,this paper mainly carries out the research on the modeling of the traction power supply system,the modeling of traction load,the power flow analysis method of traction network and the harmonic characteristics of traction network of AC-DC locomotives.The details are as follows.(1)According to the load characteristics of electric locomotive,the static load model and the dynamic load model of traction load are established.The static model includes polynomial load model and power function model.In this paper,the method of dynamic modeling of traction load is studied,its force is analyzed,its power equation is established,and its dynamic load model is obtained.Based on the composition of traction load,a comprehensive load model of "traction motor parallel induction motor and static load" is proposed to model the traction load.(2)Aiming at the constant power model and polynomial model of static load model,the influence of model parameters on voltage stability is simulated and analyzed by P-V curve method.The dynamic load is simulated by Matlab/Simulink and its running process is analyzed.Combined with the previous research,the traction power supply system and constant power load simulation model are built in Matlab/Simulink.On this basis,the constant power load model and polynomial model are used to analyze the static power flow of the traction network.The dynamic power flow analysis method of traction network is studied,and the simulation results are compared with the literature values.The results show that the comprehensive load modeling method and power flow analysis method adopted in this paper are feasible and accurate.(3)Based on the analysis of the harmonic transmission theory of traction network,the harmonic characteristics of AC-DC locomotive traction network are simulated and analyzed.The simulation models of traction power supply system,AC-DC locomotive and AC-DC-AC locomotive are built based on Matlab/Simulink,and their harmonic characteristics are analyzed to verify the correctness of the model.The effects of the length of the traction network,the position of the locomotive and the parameters of the locomotive on the harmonic characteristics of the traction network are analyzed.The longer the traction network,the higher the harmonic distortion rate of the first terminal current and the lower the resonance point.The farther the locomotive is from the traction substation,the higher the harmonic distortion rate of the head end current.The harmonic distortion rate of head end current decreases with the increase of locomotive power.The regenerative braking energy of AC-DC-AC locomotive is used by AC-DC locomotive.