A Novel Cascaded Multilevel Inverter and Modular Multilevel DC Transformer-Based Solid-State Transformer for Distribution Networks

The increasing complexity of modern distribution networks necessitates advanced and efficient power conversion systems. Solid-State Transformers (SSTs) play a crucial role in modern power systems comparing to the traditional low frequency transformers by offering significantly higher power density, compactness, and multi-functional capabilities such as reactive power compensation, voltage regulation, which are critical for smart grid application and renewable energy integration. However, conventional Cascaded H-Bridge (CHB)-based SSTs face challenges such as high cost, increased losses, and increased component count due to the use of multiple high-frequency transformers (HFTs) and related components in each submodule. To address these issues, this paper presents a novel SST topology that integrates a Cascaded Multilevel Inverter (CMI) with an Isolated Modular Multilevel DC Transformer (IMMDCT). By reducing the number of HFTs to one per phase and simplifying the design, the proposed topology lowers system costs and losses, and reducing component count while providing the four ports. Simulation results conducted in MATLAB validate the performance of the proposed topology for modern distribution networks.