Three-Level SiC DC–DC Converter With Midpoint Voltage Self-Recovery for Energy-Storage Trams

The energy-storage tram places high-quality requirements on the power supply system of its energy-storage devices. The charging system for the energy-storage tram must deliver high voltage and high power to meet the demands of fast charging. The adoption of three-level DC–DC converters and wide-bandgap semiconductor devices, such as silicon carbide (SiC) MOSFETs, expands the range of blocking voltage and switching frequency, making them highly suitable for high-voltage and high-power applications. To achieve a lightweight charging system, this article proposes a three-level asymmetric hybrid clamped DC–DC converter. The operating principles and input midpoint voltage self-recovery mechanism are introduced. By employing a “series charging and parallel discharging” circuit configuration, midpoint voltage balance can be achieved under specific conditions. A charging control algorithm is designed to meet the charging requirements of energy-storage trams. Based on this topology, a prototype charging module utilizing SiC MOSFETs devices was developed. Compared to the previous generation of charging systems, this module has reduced volume by 32.85% and mass by 30.70%. Simulation and prototype experimental results validate the self-recovery capability of the midpoint voltage under specific conditions and demonstrate the effectiveness of the proposed control strategy.