Study On The Power Supply Capacity Of Urban Rail Transit Three-phase Ac Traction Power Supply System

In the current railway development of China,the power frequency single-phase AC power supply system is generally used in the main railway,while the power supply system used in urban rail transit is DC power supply.The voltage level is low,but more serious impurities will be produced in the DC power supply system.In addition,most of the existing arterial railways and urban railroads use overhead contact networks for power supply.This form of traction network will occupy a larger space and require a large tunnel section,thereby increasing the difficulty and cost of construction.The three-phase AC traction power supply system described in this article uses power supply rails for power supply.This power supply rail set at the bottom of the train reduces the complexity of the contact structure and gives full play to the advantages of three-phase AC power in rail transit.At the same time,the system uses the power rail to supply power,and the contact structure does not take up additional space.When the third rail power supply mode is used,at complex turnout intersections,the third rail cannot be installed due to the tight arrangement of the traffic rails.As a result,the power is cut off when crossing the turnout,and the power supply rail is set under the train,and there will be no complicated intersection of the driving rails,and the switch can be continuously powered through,which can well suppress the stray current and reduce the step voltage.This article mainly studies the power supply capability of this three-phase AC power supply system.Firstly,the structure of three-phase AC traction power supply system of urban rail transit is introduced in this paper,the structure of three-phase cable power supply network,threephase traction network and the calculation method of impedance admittance parameters are introduced,the impedance of traction network is obtained based on ANSYS/Maxwell simulation platform.Then,the calculation methods of current distribution and voltage loss of traction network are analyzed,and the three-phase cable and the power supply voltage level of the traction network are compared and analyzed.Then,the design principles and methods of traction substation are determined,and the three-phase AC system is designed based on the subway line in a city,and the traction network voltage is calculated.In the end,the simulation model of three-phase traction power supply system is built based on Matlab/Simulink simulation platform,the current distribution law is verified,and the voltage simulation results are compared with the calculation results,and the current carrying capacity of the cable was calibrated.The voltage of three-phase cable and current to ground when the system is unloaded are obtained by simulation.The traffic volume meeting the voltage requirements analyzed when the traction network is disconnected,and the maximum power supply distance in the case of three-phase AC power supply is obtained.The power supply capability of three-phase AC power supply system and single-phase AC power supply system is compared.