A power quality management system of electrical railway based on YNVD balance transformer is proposed.By using the delta connected secondary taps of YNVD balance transformer

together with the coupling transformer installed at the V-shape connected secondary side

an electric interface for a single-three phase back-to-back converter is provided. Compared with the traditional back-to-back converters

the proposed three-phase converter has more complex topology than single-phase one

while it only needs one coupling transformer

so that the disadvantages of the proposed system can be faded. Meanwhile

in order to keep the system compensation capacity

the three-phase converter can not only degenerate into single-phase converter on the malfunction of the c-phase bridge arm but also operate independently with the malfunction of single-phase inverter

which ensures the high reliability of the proposed system. Based on the theoretical analysis

a simulation model is built with MATLAB

and a small-capacity prototype is established. Both the simulative and experimental results verify the effectiveness of the proposed system.