基于FDTD接口方法的ZPW-2000轨道电路暂态分析

轨道电路在列车驶入/出清时存在暂态过程，可以利用接收端信号的暂态突变对轨道电路的状态进行判断. 时域有限差分（finite-difference，time-domain，FDTD）方法是求解传输线的常用数值解法，但ZPW-2000轨道电路结构比一般轨道电路更加复杂，直接采用FDTD法并不适用. 基于此，提出了一种基于FDTD和ATP-EMTP（alternative transients program-electromagnetic transients program）接口模型的ZPW-2000轨道电路暂态分析方法. 该方法将整个模块分为传输线与集中参数网络两个部分，其中，传输线采用FDTD求解，集中参数网络在ATP-EMTP中计算，两个部分用受控电流源关联. 对ZPW-2000轨道电路的仿真结果表明:道床电阻和分路电阻对接收端信号幅值有较大的影响，当道床电阻降至0.6 Ω?km时接收端电压从2.0 V下降到0.5 V左右，当分路电阻增至0.2 Ω时接收端残压达到了1.0 V左右，此时若仅采用门限比对的方法难以区分轨道电路的状态；然而，在列车驶入/出清的瞬间，接收端信号存在暂态突变，可根据突变特性实现轨道电路分路态的检测. 

Transient Analysis of ZPW-2000 Track Circuit Based on FDTD Interface Method

A track circuit performs a transient process when a train enters or departs a section. Therefore, its circuit state can be judged by the transient change of signals at the receiving end. The finite-difference, time-domain (FDTD) is a common numerical solution for the transmission line. However, the structure of the ZPW-2000 track circuit is more complex than that of general ones. Thus, the direct FDTD method does not work well. Therefore, an FDTD-based transient analysis method and an alternative transient program-electromagnetic transients program (ATP-EMTP) interface model for a ZPW-2000 track circuit is introduced. The entire module is divided into two parts: transmission line and centralised parameter network. The two parts are related by a controlled current source. The transmission line is solved using FDTD, and the centralised parameter network is solved using the ATP-EMTP. The simulation results of the ZPW-2000 track circuit show that the ballast and shunt residences have great impacts on the receiving-end signals. When the ballast resistance falls to 0.6 Ω?km, the receiving-end voltage drops from 2.0 V to about 0.5 V; when the shunt resistance increases to 0.2 Ω, the residual voltage at the receiving end rises to about 1.0 V. If only the threshold comparison method is used, the state of the track circuit is indistinguishable. However, a transient mutation ccurs in the receiving-end signals when the train enters or departs. This can be used to determine the shunt state of the track circuit.