Current-Carrying Mechanism of New Continuous Cable Traction Power Supply System

Continuous cable traction power supply system is free of electrical phase separation and extend power supply distance, dealing with power quality problems effectively. However, cable traction network (CTN) contains different voltage levels, and the fundamental frequency current flows every CTN link before being used by trains. Moreover, the harmonic current transmitted from trains needs to penetrate in two voltage levels before feeding back to utility grid. In order to study current-carrying mechanism in novel continuous cable TPSS, starting from the special topology of CTN, the equivalent circuit of train-CTN coupling system is established according to dual-port network analysis method. Then current transmission rules in CTN are analyzed. Combined with simulation model, the harmonic current distribution in CTN and harmonic current content of main substation (MSS) are studied. When the new system contains eight short sections for one train, the fundamental frequency current is mainly transmitted by the single-sided CTN where the train locates, and the current ratio between load and MSS is less than four (traction transformer ratio). The harmonic current content of MSS decreases by 43.5% compared with harmonic current content at train.