Optimal Location of Passive Filters for 25 kV AC Railway Traction Network

ABSTRACT

This study investigates the improvement railway network Power Quality (PQ) parameters by optimal passive filter placement in railway traction networks. A MATLAB Simulink model of a traction network with fixed loading and three tuned filters (tuned to third, fifth, and seventh order harmonics) is developed. Simulations are conducted for each filter at different locations, and a mathematical model is created to evaluate filter efficiency. Results from both methods show that higher‐order filters (fifth and seventh) have negligible location‐dependent effects. Optimal filter placement is determined by simulating fifth and seventh order filters at the transformer location and varying the third harmonic filter location. The study evaluates PQ parameters, including current harmonics, voltage profile, and voltage harmonics, and finds significant improvement when filters are placed in the mid‐point of the traction network (section). In general, in the distribution network of power system filters are placed either at load end or source end based on the aim of the filter. In Railway networks this study becomes relevant because the load location is varying, impedance of traction line and transformer are in same range resulting in considerable line harmonic voltage drop. Moving the third harmonic filter to a 10–20 km range (away from traction transformer) improves the voltage drop by 2.3%, voltage THD by 2.4% at tail end which is within the recommended limits in IEEE 519–2022 and no major change in voltage drop, voltage harmonic and current harmonics at the source end.