Abstract: Traditional traction power supply system exists quality problems such as reactive power, unbalance and harmonics. Moreover, the multiple substations cannot be interconnected, which seriously restricts the development of high-speed and heavy-load trains. To solve these problems, this paper proposed a two-phase to single-phase converter which is suitable for the existing traction substation to achieve advanced cophase supply system. The DC-link voltage ripple was analyzed, and the boundary of DC-link capacitance was calculated. In order to suppress the influence of imbalance load of the two-phase converter on three-phase grid, a two-phase balanced power control strategy was proposed. Finally, based on the YNvd traction transformer, the feasibility of the proposed topology and control strategy applied to the advanced cophase power supply system was verified by simulation and experiment.