Modeling and Simulation of Railway Power Supply Systems for a Substation- Case of Addis Ababa-Light Rail Transit Kality Depot (NS6) Substation

Abstract

This document explains about the MATLAB simulation report on kality traction substation of Addis Ababa Light Rail Transit (AA-LRT). AALRT is a fully electrified metro line erected from North to South, and East to West directions of Addis Ababa city. EEPCO (Ethiopian Electric Power corporation) is the power supplier to this transit operator. The electric power provided by EEPCO passes a series of steps to make it suitable for feeding the railway line. For conversion of electric power from one form to another a substation is needed. Similarly, AA-LRT deploys rectifier substations (SS) to convert three phase, 15KV, 50Hz AC to 750-900 V DC voltage. Since one of these type substation feeds about 1.5 to 2 kilometers railway line. AA-LRT has more than 15 substations of this kind. Of those substations have more or less same nature. On this project the rectifier substation of AA-LRT found at kality depot named NS6 SS is chosen to be simulated on MATLAB/SIMULINK. As mentioned above the purpose of these substation is to convert three phase 15KV, 50 Hz AC to 750V-900 V DC catenary voltage. On developing the simulation diagram basic power system components like voltage source, transformer, power diode is used by picking from SimScape library of MATLAB. Commonly used blocks are also used for measurement and display of power system parameters. Some power system components not available at library, or found at the library but not suitable for this simulation purpose are newly modelled. Voltage transformation, AC to DC rectification as well power system protection and optimization operations are generally done on this simulation. Finally, all the elements of the SS are logically connected on the SIMULINK model, then the three phase 15KV, 50Hz AC has been able to be converted to 750-900 V DC voltage to feed the railway line. There happens some challenge on specifying rating of components and optimizing the behavior of some power system parameters while developing as well analyzing the simulation for this substation.