Voltage Self-Balancing Analysis of Indirect Series-Connected SiC MOSFETs for Electric Vehicle Fast Charging

Under the demand of electric vehicle DC fast-charging stations for medium-voltage DC–DC converters, the indirect series-connected hybrid clamped topology based on quasi-two-level (Q2L) modulation demonstrates significant application potential due to its balanced advantages in cost and performance, as well as its inherent voltage self-balancing capability. However, a unified analytical framework for the voltage self-balancing mechanism of the hybrid clamped topology under different Q2L modulation strategies has not yet been established, which limits further topology optimization and broader application expansion. To address this issue, this paper first investigates the key factors influencing voltage self-balancing and conducts a comprehensive analysis of the self-balancing behavior under different Q2L modulation strategies, thereby deriving the conditions required to maintain the self-balancing capability of the hybrid clamped topology. On this basis, an improved Q2L modulation method is proposed to ensure stable and reliable voltage self-balancing performance. Finally, both the simulation and experimental results verify the accuracy of the proposed analysis method and the effectiveness of the improved modulation strategy.