Simplified Soft-Switching Constraints for High-Power Multi-Active Bridge Converters

A multi-active bridge (MAB) dc-dc converter, utilizing its multi-winding transformer, enables flexible power flow between multiple dc sources with minimized system components and power conversion stages. However, when voltage ratios among the multiple dc sources are mismatched, the efficiency deteriorates due to limited soft switching capability and increased reactive currents. Therefore, numerous modulation schemes have been developed, but the extensive degrees of freedom in duty cycle and phase-shift adjustments complicate their design. For simplicity, straightforward sufficient conditions have been used in some modulation designs to achieve soft-switching and compress the degrees of freedom to unity. However, these simplified soft-switching constraints have mainly been applied to single-phase MAB converters and not been fully addressed for three-phase MABs, which are emerging for high-power applications. This article extends these simplified soft-switching constraints from single-phase to three-phase MABs. Flux-domain analysis is presented to utilize the key principles of the single-phase MAB constraints and to adapt them for the three-phase configuration. ... mehrThe validity of the extended soft-switching constraints is demonstrated through experimental results.