Cophase Traction Power Supply System Based On Back-to-back HVDC Transmission Technology

Electrified railway in our country is developing very fast,so the research of traction power supply system is popular. At present,China’s railway electrification use different-phase power supply system,which have some problems:the system’s negative sequence current、 harmonic wave and etc.The reason is that three-phase system supply the power to train with single phase,which makes the supply arms of adjacent substations are in different phase. Power supply sections need to use neutral section insulator.In this situation,electric locomotive wiil confront the danger of passing the phase-separating section without power or rushing with power when it’s in operating process.Both of them have seriously impact on the safety of locomotive running.So in this case,the traction power supply system requires a reasonable transformation in order to solve the current problems.The contents of this paper are:cophase traction power supply system based on back-to-back HVDC transmission technology.Cophase traction power supply system can achieve single-phase power supply with AC27.5kV,which can solve most of the current problems in traction network.First of all,this paper do the research on that if back-to-back HVDC transmission technology is a feasibility study on the application of traction system,work out the basic network topologies,including DC converter rectifier side,inverter side, and grid connection control part,then established the mathematical model of each part.The principle is putting110kV/66kV three-phase current into transformer,then go through back-to-back converter station,transform into27.5kV single-phase AC power,and with the help of the grid connected device to accomplish the cophase traction power supply system.According to the topology of each part and the whole cophase traction power supply system establish simulation model,the simulation results show that,the model established is reasonable and feasible in technology. Finally,analyse the tidal current in traction condition of the cophase traction power supply system,obtain the power flow distribution characteristics and the basic law,the results show that the construction of the traction power supply system based on back-to-back HVDC transmission technology is feasible in technology,while it can provide reference for engineering application.