In recent years, full-bridge MMC has gained more and more attention due to its DC fault ride-through capability. However, at present, most of the research on the full-bridge MMC is to make the sub-module work in the mode of outputting only positive level (or negative level) and zero level, and there are normally on-off and on-off switches in the sub-modules, which leads to uneven distribution of internal loss of sub-modules, and is not conducive to the design of heat dissipation system. In order to optimize the energy distribution in the sub-modules, the full-bridge sub-modules are studied firstly, and the output voltage of the sub-modules is analyzed based on the carrier phase-shifting modulation. Secondly, the single-phase MMC is modeled and a closed-loop modulation strategy which can flexibly adjust the working state of the sub-modules is derived. Finally, PLECS software is used to simulate the modulation strategy proposed in this paper.