Star-Connection Supercapacitor-Embedded CHMC-Based STATCOM for Electrified Railways

The split energy storage-embedded modular multilevel converter has emerged as a promising solution to address energy efficiency and power quality concerns in electrified railways. However, the intricate system topology and coupled control objectives of the existing ones aggravate the reliability and flexibility. To address these challenges, a star-connection supercapacitor-embedded cascaded H-bridge multilevel converter (SCCHMC) STATCOM is proposed in this article. The proposed configuration offers advantages as it requires fewer power cells, enhancing reliability while reducing costs. To facilitate the flexible control of multiobjective, including regenerative braking energy utilization, negative sequence current suppression, and reactive compensation, a sequence components-based decoupling control is developed for the SCCHMC-STATCOM. The proposed method features straightforwardness and flexibility, with its effectiveness validated through experimental results. Additionally, a comprehensive discussion regarding fault protection and a comprehensive comparison between the proposed SCCHMC-STATCOM and the state-of-the-art energy storage-based solution for railway applications are conducted.