Modular Multilevel Converter with Interleaved Submodule based on Current-Fed Dual Active Bridge

This paper proposes a novel architecture for a solid-state transformer (SST)-based modular multilevel converter (MMC) incorporating a dual active bridge (DAB) stage within each submodule (SM). The proposed converter features interleaved SMs that concurrently interface with the converter AC side and serve as the input-side bridges of embedded current-fed DAB (CF-DAB) converters. By integrating the CF-DAB topology directly into the MMC SMs, the proposed design achieves higher power density, reduced component count, and improved scalability for medium- to high-voltage DC applications, while also enabling a distributed architecture. The interleaved structure among SMs facilitates ripple current minimization, extends the soft-switching operating range, and increases the number of effective voltage levels. This paper provides a comprehensive analysis of the converter operating principles, modulation strategies, and coordinated control between the MMC and CF-DAB stages. The validity and performance of the proposed concept are demonstrated through detailed simulation results.