Model-Free Approximate Fundamental Reactive Power Minimization for Modular Multi-Active Bridge Converter

Modular multi-active bridge (MMAB) converter is widely used in modern power grids to provide multiple ports for flexible power conversion and interconnection among grids, loads, and electric vehicles, etc. However, MMAB converters adopting traditional single phase-shift modulation are facing low-efficiency issues within a wide operation range. In order to address online optimization concerns brought about by the strong coupling of the converters, this paper proposes an optimization strategy to approximately eliminate the overall fundamental reactive power of MMAB converters without accurate model parameters, thus reducing the root-mean-square inductor currents and the overall conducting loss. The proposed optimization strategy is based on frequency domain and can be extended to multi-active bridge converters as well. Finally, the feasibility and the effectiveness of the strategy have been validated on a 4-port MMAB converter.