Abstract: This paper proposes an MMC-DC/DC-type medium-voltage DC self-powered topology, which consists of two-stage circuits: a medium-voltage power extraction circuit and a low-voltage power supply circuit. The front-stage medium-voltage power extraction circuit adopts a modular multilevel structure, with half-bridge submodules connected in series on the upper arm and chopper submodules connected in series on the lower arm. The rear-stage low-voltage power supply circuit employs an isolated DC/DC circuit with input-series-output-parallel configuration. Based on the analysis of the working principles of the front/rear-stage circuits, the resonant parameters of the arm inductor and submodule capacitors are optimized using the Sparrow Search Algorithm. To address the mismatch issues of magnetizing inductance and turns ratio parameters in the ISOP-structured isolation transformer, a power self-balancing method based on master-slave control is proposed to achieve input voltage balancing and output current equalization in the subcircuits. The feasibility of the proposed topology and control strategy is verified through theoretical analysis and simulation.