Comparative study on the position of shunt active power filters in 25 kV AC railway systems

AC electrified railway systems show power quality problems such as harmonic current pollution, feeder voltage perturbation, and reactive power demand. These power quality problems have a bad effect on the AC railway system itself as well as other electric systems connected together. This paper investigates comparatively two configurations of a shunt active power filter (SAPF) for improving power quality in the AC railway systems. Different control algorithms corresponding to the installation position of the active power filter at the substation or at the sectioning post are proposed respectively. A comparative case study on the two positions of SAPF has been performed comprehensively.