For the present problems brought about by modular multilevel DC-DC converter topology and its AC balance control idea

a novel module multilevel DC-DC converter topology based on the DC control idea is proposed. By reconstructing the full-bridge submodules

each submodule capacitor contains two charging and discharging paths. The capacitors can perform power transfer and voltage self-balance through a local parallel branch formed between adjacent submodules

so as to avoid the voltage unbalance of the capacitors in the unidirectional DC power conversion. The analysis and simulation test of the balance mechanism and the basic principles of the converter show that the proposed converter can operate stably in the DC control mode

the capacitor voltage can be self-balanced

the conversion ratio is big and has the potential to be used in the different applications of DC transmission and distribution. This work is supported by National Natural Science Foundation of China(No. 51490681)and National Basic Research Program of China(973 Program)(No. 2015CB251004).