In this paper, a combined AC-DC power flow model is purposed for the existing AC distribution system, where a certain amount of DC is superimposed from the battery swapping station on the usual AC feeder line with the help of a proposed zig-zag transformer. In the proposed feeder system, the line-to-line voltages will be pure AC, hence all the three-phase balanced load can be directly connected through lines. But, the line to ground voltages will be shifted upward, as same as the amount of DC voltages imposed by the battery swapping station which is demanded by the distribution system operator. To support the proposed methodology, power transmitted through different levels of distribution lines (33 kV, 11 kV, 400 V) is analyzed theoretically and numerically and simulated on MATLAB/Simulink Further, the proposed system is validated through small scale prototype designed and performed in the laboratory. The obtained results show the significant enhancement of the power flow capability such as up to 118.3% capacity improvement in the case of 400 V line. This purposed distribution model is a new subject that has great economic efficiency with the availability of DC sources such as battery storage plant to grid. It provides direct access to both AC and DC loads in the distribution system.