Research On Optimization Design Of Long Distance Power Supply Scheme For Plateau Electrified Railway

The plateau area of our country is limited by the condition of power grid frame,and there are few power points available along the electrified railway.The power supply capacity is relatively weak,and the traction load will produce power quality problems based on negative sequence in the power grid.In addition,the road conditions in the plateau area are complex and the growth slope is more,which leads to the difficulty of setting the electric separation phase.At present,the electrochemical expansion of Qinghai-Tibet railway Golmud-Lhasa section,the China-Nepal Railway and the Sichuan-Tibet Railway projects are being planned and built.It is of great theoretical significance and application value to optimize the long-distance power supply scheme of plateau electrified railway,reduce the number of traction substation and sub-phase setting,and improve the matching relationship between traction power supply system and external power supply.First of all,taking the China-Nepal Railway,which is being planned and built in our country as an example.This paper studies the matching between external power supply capacity and traction load demand from the aspects of the present situation and planning of the power grid in Tibet,the power supply capacity of different voltage grade power grids and the scheme of access to external power supply.The long-distance power supply scheme of Plateau electrified railway is put forward.Through the comparison and selection of technical economy,the technical route of using dual-core cable for traction network under direct supply mode is determined.And the equivalent circuit characteristics of traction power supply system are analyzed.Secondly,based on the simulation software of MATLAB/Simulink,the simulation model of long-distance power supply system using dual-core cable is established under the direct supply mode.The power supply distance of the power supply scheme under different driving densities is simulated and analyzed in order to verify the superiority of its power supply capacity.At the same time,according to the voltage uplift effect of the Ferranti effect of cable traction network in long distance power supply,the influence of cable length,reactive power compensation coefficient and leakage resistance of traction transformer on Ferranti effect is studied.Then,taking the minimum voltage of the catenary as the constraint,the conventional power supply scheme of China-Nepal Railway is optimized by long-distance power supply technology.The number of traction substation and electric phase is reduced,and the adaptability to external power supply and line condition is better.At the same time,with the goal of setting the minimum number of traction substation,the configuration scheme of traction power supply system to meet the demand of traction load is given.Finally,the influence of different power supply schemes on the power quality of external power supply is evaluated from three aspects of voltage deviation,three-phase voltage unbalance degree and harmonic voltage comprehensive distortion rate.Aiming at the power quality problem dominated by negative sequence,based on the comprehensive compensation model of combined phase power supply technology,the compensation effect is verified by simulation.And the capacity configuration of traction transformer and compensation device is given,which provides technical support for the application of long-distance power supply technology in Plateau electrified railway engineering.