A Medium-Voltage Four-Port Energy Router Based on Modular Magnetic-Coupled Converters (MMCC) With Reduced Switching Losses

The medium-voltage (MV) energy router is challenged by the construction of multiple isolated ports with high-power-conversion efficiency. In order to overcome these challenges, this article presents a modular magnetic-coupled converter (MMCC). It utilizes transformer-centered dc-dc stage and ac-interface circuits to fabricate isolated dc and ac ports. This fully isolated configuration is also assisted by resonance and quasi-resonance operations to enhance the power efficiency. Moreover, the synchronously resonance operation of the ac-port-inked half-bridges in dc-dc stage enables the impedance-minimization for magnetic-coupled channels, leading to the spontaneous cancellation of double-line-frequency fluctuations among three phases and auto-balanced dc-link voltages even across modules. The quasi-resonance operations of the dc-port-served half-bridges facilitate the dc voltage adjustment or power flow management. Both the resonance and quasi-resonance operations help reduce the power losses by more than 4% under heavy load condition. The feasibility of the proposed MMCC-based four-port energy router is verified by 10-kV 1-MW simulations and 190-V 1-kW experiments.