| The power supply reliability and power quality of have always been important factors for the safe and stable operation of electrified railways.A key link of analyzing the power quality of electrified railways is to conduct research of electromagnetic transient simulation.As an important part of the traction power supply system,the traction network is different from the power system with symmetric and unified transmission line structure.Its structure is more complex,the cross sections of the contact line and rail shaped,and the rail materials ferromagnetic-nonlinear.All these features make the current used simulation software such as EMTP and MATLAB unable to be accuratly adapted to the complex and changeable traction network structure and element model in the traction power supply system.Therefore,it is of great significance to study electromagnetic transient simulation models and algorithms for traction networks.In this paper,first we discuss the construction of the chain network of the traction network.For the calculation of electrical parameters of the traction network,the calculation methods of the internal impedance of various conductors in the traction network are summarized by categories.For the rail,the common P60 type rail is used to test the magnetic properties of the material.The test results include the basic magnetization curve,hysteresis loop,and coercivity of the rail.The above data is used in the 1: 1 simulation in the ANASY Maxwell software Modeling to calculate the parameters of the frequency-varying impedance of the rail.On this basis,the multi-conductor transmission line model of the traction network is constructed by wire equivalent merging and phase-mode conversion,and the frequency-variable impedance and admittance parameter matrix of the traction network in the direct power supply mode are calculated to provide basic data for the transient calculation of the traction network.Then based on the existing frequency-change transmission line model solution theory,the solution algorithm of the established traction network frequency change multi-conductor transmission line model is analyzed.The J.Marti frequency variation model solution theory is selected as a reference.The key to modeling is to accurately and rationally fit the characteristic admittance and weight function in the complex frequency domain.In order to improve the accuracy of the fitting result,the genetic algorithm is used to optimize the initial pole for the characteristic that the initial pole greatly affects the matching result.Then from the theoretical point of view,the recursive convolution is used to solve the electromagnetic transient,the convolution formula deduced,and the coefficient calculated.Finally,based on the above research of parameter calculation method,theory of model construction and algorithm,the flow logic of the electromagnetic transient calculation of the traction network is collated and designed.The program is written in the Visual Studio development platform using c# language.The program can be used to calculate the impedance frequency-dependent parameter matrix,fit the characteristic admittance and weight function,and solve the transient state.Taking the closing transient of the traction network as an example,the transient calculation is performed to verify the feasibility of the program. |
