Intra‐Phase Proportional Submodule Voltage Balancing in Modular Multilevel Converters for MV Ultra‐Fast EV Charging Applications

ABSTRACT

This paper proposes an advanced modular multilevel converter (MMC)‐based topology specifically developed for medium‐voltage (MV) grid‐connected ultra‐fast electric vehicle (EV) charging applications. A new intra‐phase proportional balancing via d/q injection (IPB‐DQI) strategy is proposed for MMCs, achieving robust submodule (SM) voltage balancing through intra‐phase proportional feedback and implicit generation of circulating currents without added computational complexity. The developed solution maintains stability at 600 V per SM, supporting a 2.4 kV MVDC link using cost‐effective 750 V SiC MOSFET devices based on proven derating practices. Key operational metrics include consistently high‐power quality, minimal harmonic distortion in both current and voltage and stable unity power‐factor operation across varying loads. The enhanced balancing approach significantly mitigates capacitor voltage fluctuations, improves robustness, reduces switching‐device stress and enhances the system's overall efficiency and reliability. Comprehensive validation of the proposed topology was conducted through real‐time performance testing using an OPAL‐RT experimental setup across different case studies. In addition, results from the OPAL‐RT and TI DSP (TMS320F28379D) embedded controller hardware‐in‐the‐loop experimental setup confirm that the proposed balancing method effectively ensures stability, dynamic performance and robust grid integration. This makes the system well‐suited for scalable deployment in industrial‐level fast‐charging infrastructures.