Solid-State Transformers Connected to 6.6-kV Distribution System in Japan

This paper presents research on Solid-State Transformers (SSTs) conducted under a MEXT project in Japan. The proposed SST interfaces 6.6 kV medium-voltage grids with 200 V low-voltage networks, using SiC and GaN devices in a modular multilevel converter topology. The paper introduces the development of a high-efficiency low-voltage inverter utilizing GaN devices. Additionally, this paper presents a methodology for determining optimal battery capacity based on demand fluctuations and renewable energy output analysis. This research contributes to advancing SST design and implementation in smart grid applications, providing insights for next-generation power distribution systems.