Study On Mathematical Model And Short-circuit Current Calculation Of DC Traction Power Supply System

With the development of the national economy and the increase of the traffic, as a new traffic facility, urban rail transportation is used more and more widely. The next few years will become the significant time of the urban transportation. The research on the calculation of short-circuit current in DC traction power supply system is becoming the researching hotspot on international and native.The calculation of short-circuit current in DC traction power supply system is important for the designing of mass transit power supply system. It is not only the basis for the reasonable selection of DC quick switch and design of DC protective-relay device, but also an important judgment for the estimation of the whole system's safe reliability and the decision of traction substation's operation mode.Firstly this paper discussed the calculation method of running rail and contact rail's DC resistance with the third rail feeding system, then studied the calculation method of rail's internal inductance and supply circuit's external inductance, thus the inductance parameter of running rail and contact rail under 50Hz was deduced, moreover the inductance parameter was compared with the measure data to validate its veracity.This paper analyzed the principle of rectifier in DC traction substation and polygonal external characteristic model of rectifier in detail, then replaced DC traction substation by Theremin's equivalent circuit which consisted of ideal voltage source and the internal resistance, sequentially established the mathematical model of DC power supply system, meanwhile designed the calculation program and interface of steady-state short-circuit current on zero fault impedance of DC tractive network. What's more, the conclusion was compared with the measure data of metro line to validate its veracity. At last, this paper not only established the simulation model of DC power supply system with 24-pulse rectifiers included by using power system module in SIMULINK, but also simulated and analyzed the transient short-circuit currents when a contact rail short-circuit occurred at different positions, this can reflect the transient process of short-circuit currents accurately.