Comprehensive Comparison of the Single-Phase and Three-Phase Unidirectional DC/DC Converters for High-Power Medium-Voltage Applications

This paper presents a comprehensive evaluation and comparison of two isolated unidirectional DC/DC converter topologies – the single-phase Phase-Shifted Full Bridge converter (PSFB) and the three-phase DC/DC converter (3-ph DC/DC), for high-power applications such as MVDC collection grids. The operating principles and key differences between the two converters are presented in detail. Imposing identical technical specifications, the two converters are optimized separately, considering the performance of the switching stages under a wide range of operating conditions. The optimal designs are then juxtaposed, clearly showing the design trade-offs between the two topologies, including the Medium Frequency Transformer (MFT) and output filter design. The implications of the wide input voltage regulation range on the performance are discussed in detail, and the dynamic behavior under closed-loop control is shown through simulations and validated on reduced-scale converter prototypes.