An SOS2-based moving trains, fixed nodes, railway power system simulator

This paper presents and proposes an optimization model for railway power supply system simulations. It includes detailed power systems modeling, train movements in discretized time considering running resistance and other mechanical constraints, and the voltage-drop-induced reduction of possible train tractive forces. The model has a fixed number of stationary power system nodes. The proposed model uses SOS2 (special ordered sets of type 2) variables to distribute the train loads to the two most adjacent power system nodes available. The impact of the number of power system nodes along the contact line and the discretized time step length impacts on model accuracy and computation times are investigated. The program is implemented in GAMS (General Algebraic Modeling System). Experiences from various solver choices are also presented. The train traveling times are minimized in the example. Other studies could, e.g. consider energy consumption minimization. The numerical example is representative for a Swedish non-centralized, rotary-converter fed railway power supply system. The proposed concept is however generalizable and could be applied for all kinds of moving load power system studies.