A Simplified Modular Multilevel Step-Down DC/DC Converter for Medium to High-Voltage Applications

DC/DC converters are essential in DC microgrids for interfacing DC generation and loads to the DC bus. Conventional DC/DC converters are, however, unsuitable for medium/high-voltage conversions, due to semiconductor restrictions and filtering requirements. Modular DC/DC topologies, mainly based on the modular multilevel converter (MMC), have been proposed to cover this application range. This paper introduces a hybrid modular DC/DC step-down converter suitable for medium/high-voltage systems, which includes only one arm of series-connected submodules (SMs) and offers distinct advantages over existing designs. These include a reduced number of series-connected semiconductors and SMs along with fewer SM capacitors, which lowers cost, size, and complexity, while also simplifying capacitor voltage measurement and balancing. The converter operates without circulating currents between different arms, enabling simpler control and excellent dynamic response to reference voltage or load changes. Simulation results in MATLAB/Simulink are included to demonstrate the above features.