Research On Modeling And Harmonic Characteristics Of Traction Power Supply System Based On Train-Network Coupling System

In recent years,with the rapid development of China’s electrified railway,the harmonic problem of traction power supply system has been paid more and more attention.The large number of field test data needed for harmonic control or monitoring and evaluation of the traction system is often limited by the limited field of the harmonic monitoring device,which is very limited and difficult to meet the demand of harmonic characteristics study.Therefore,it is necessary to establish a coupling and dynamic simulation of the traction power supply system with electric locomotive,and a large number of different conditions under the simulation calculation for the traction system harmonic analysis to provide an important source of data is very necessary.At first,perform mathematical modeling for the important components of the traction network,including traction substation,traction network and electric locomotive in the paper.The different wiring modes of traction transformers are discussed,and relationships of the three-phase to two-phase for voltage and current transformations are discussed.The theory of Carson and matrix transformation are used to merge and reduce of the traction wires.The method of least squares is used to improve the way by using piece wise linear,which is used to fit the no-load characteristic curve of traction motor for electric locomotive.Secondly,a traction power supply system simulation of a traction substation in a in Shan,xi Province is established by using PSCAD software,and the validity of the model is verified by the measured data of the traction variable.Then,the simulation model is used to analyze the harmonic characteristics of the traction system into the power system under different traction conditions including the locomotive level and the speed,the locomotive position,the length of the traction wire and the connection mode of the traction transformer.In addition,the voltage level of the traction network is also one of the important criteria for measuring the quality of traction power supply.In this paper,the distribution of the voltage at the points of the traction network with a direct supply with a negative feed mode and auto transformer(AT)power supply of the traction network is analyzed.Based on the characteristics of the resonance of the traction network,the relationship between the locomotive current and the harmonic current of the low-voltage side of the traction transformer is analyzed theoretically.The results compared by the harmonic content and the amplitude simulation,shows that the traction network does have some harmonic amplification,which is consistent with the theoretical analysis.Finally,aiming at the need of harmonic control for traction power supply,a harmonic control scheme using parallel hybrid filter is proposed and simulated by PSCAD.Theresults show that the voltage and current harmonics of the three-phase system are greatly reduced after adopting the parallel hybrid filter,which can meet the demand of the power quality of the power system.