Constant Valley Current Control Strategy for Bridge-Type Switched-Capacitor-Based Medium Voltage DC–DC Converter Under Near Critical Conduction Mode

While bridge-type switched-capacitor-based medium-voltage DC-DC converter (BSC-MVDC) shows excellent application potential in medium-voltage DC (MVDC) distribution, achieving soft-switching operation in its key component, modular multilevel multi-port DC-DC converter (M3DC) remains challenging. Incorporating the near critical conduction mode (nCRM) concept, this paper analyzes the soft-switching characterization of M3DC under nCRM, proposes a constant valley current control (CVCC) strategy, and presents a parameter design methodology. Simulation and experiment results demonstrate that the proposed CVCC strategy enables zero-voltage-switching (ZVS) turn-on of switching devices and zero-current-switching (ZCS) turn-off of anti-parallel diodes, significantly improving converter efficiency and showing considerable engineering application value.