Research On Unified Calculation Model For Traction Supply And Stray Current Of Metro

In recent years,the rapid development of urban rail transit in China has made great contributions to easing traffic congestion and facilitating citizens’ travel.However,with the construction of metro lines in full swing,the negative impact caused by stray current is spreading from point to area and becoming increasingly prominent.In this context,considering the influence of metro depot or parking lot section structure,this paper analyzes the distribution characteristics and influencing factors of metro line stray current from a macro perspective,which has important reference value for the prevention and control of stray current.According to the composition structure of metro DC traction power supply system,considering the influence of the operation characteristics of metro depot or parking lot section and its one-way conduction device on the stray current distribution,based on the concentrated parameter model and the electric field distribution characteristics of hemispherical grounding electrode,this paper studies and establishes the metro traction power supply stray current field-circuit coupled model,and deduces the assignment modification rules of node admittance matrix elements in the case of field-circuit coupling based on the node voltage method,form a unified calculation model of metro traction supply and stray current,which lays a foundation for the calculation and analysis of metro stray current.Aiming at the modeling problem in the case of large scale or complex structure of metro model such as more line branches or long distance,this paper further studies the fast modeling algorithm based on the operation plan,studies and designs the generation method of train diagram based on single particle train motion model.With the interface parameter extracted,this paper designs the user interface and deploys the application program,constructing the metro stray current user simulation system and improving the modeling efficiency to a certain extent.Based on the proposed unified calculation model of metro traction supply and stray current,according to the structural characteristics and composition parameters of a metro depot,the stray current distribution characteristics of the metro depot are analyzed based on the continuous working condition evaluation of the first train.The results show that the one-way conduction device of the entrance/exit line located on the main road is the main switch of stray current in the depot,and its conduction mainly depends on the cathode potential of the rail connected to the main line.The rail potential caused by the operation of the main line will still act on the one-way conduction device of the entrance/exit line,so that the depot will continue to be disturbed by stray current.The influence of the depot structure shall be considered as much as possible in the analysis of the distribution of stray current on the main line.Based on the user simulation system of stray current,the distribution characteristics and influencing factors of stray current in the whole line are analyzed through the current of one-way conduction device of entrance/exit line in the section,the total amount of stray current in the line and the total amount of stray current in the section.According to the idea of control variables,the influence of traffic density,routing mode and connection position of the depot/lot section on the temporal and spatial distribution of stray current in the whole metro line is compared and analyzed.There is a nonlinear relationship between the traffic density and the total amount of stray current on the line.The routing deviation will lead to the distortion of stray current distribution in the section.The depot/lot section connected to the traction station is usually disturbed by stray current when the train on the main line is in traction,while the section connected to the ordinary station is often disturbed by stray current when the train on the main line is braking.In this paper,the unified calculation model of DC metro traction supply and stray current is studied.The coupling and unified calculation of stray current between main line and field section,train and traction network power flow are realized from the stray current aspect and power supply aspect respectively.The distribution characteristics of metro line stray current are analyzed,which provides an auxiliary idea for the calculation,characteristic analysis and influencing factors of stray current distribution of metro line.It has a certain reference value for the research and prevention of subway stray current suppression.