Modular MV Naturally Balanced Converter with High-Frequency Isolation and no DC-Link Capacitor for EV Fast Charging

This paper presents and verifies the concept of a converter for a medium voltage (MV) electric vehicle (EV) charging station that employs high-frequency galvanic isolation and features no dc link capacitor. The system is based on multi-cell boost (MCB) topology; however, instead of a conventional two-stage configuration with dc link, isolated current source converter (iCSC) based cells are used. They perform power factor correction (PFC) while also providing HF galvanic isolation and are connected in series at the input and in parallel at the output. The exceptional feature of such configuration lies in inherent voltage balancing among the cells, which significantly simplifies the control and protection and improves scalability. The concept is verified with a scaled 4 kW prototype having three iCSC cells.