In this paper, a novel power electronic transformer (PET) structure for dc power distribution system is proposed. The proposed converter can achieve very high voltage conversion ratio with high frequency isolation and bidirectional energy flow, thus it can be used as the interface equipment of high voltage and low voltage dc power grid. Different from the conventional structure, only one high frequency transformer is used in the proposed structure, reducing the fabricating cost. Based on the proposed topology, phase shift control method is introduced to output the required power and balance the submodule voltage. A 100 kW simulation model is built up in Simulink/MATLAB. The simulation results verify the proposed converter and control method.