Energy router is an intelligent power electronic device that can realize the active management of power flow and provide convenient access to distributed energy resource. This paper presents the structure of an AC-DC hybrid multi-port energy router, which acts as the interface between the power consumer and the distribution network. The corresponding coordinated control strategy is developed to guarantee the regular operation of the energy router and a mode switch strategy with advanced compensation is proposed to achieve seamless transition between grid-connected mode and islanded mode. A novel and practical fuzzy logic controller considering unit-time electricity charge is proposed for the energy router to prolong battery life, to improve economic benefits of power consumers, and to smooth fluctuations of renewable energy generation or load consumption. The simulation and experimental results have validated the coordinated control and energy management strategies and demonstrated that the energy router has satisfactory performance.

Aiming at the low-voltage DC distribution network system and combining the characteristics of F2F structure and ISOP-DAB structure DC transformer, this paper proposes a DC transformer structure based on modular multilevel converter (MMC) and cascaded H-bridge. First of all, this paper analyzes several different cases. Case 1 proposes a type of equal carrier-phase-shift pulse-width modulation (CPS-PWM) of MMC, which can produce an equal five-level voltage waveform. In the meanwhile, another unequal CPS-PWM control is proposed to produce an unequal five-level voltage waveform. According to the descriptions of case 2, the quasi-square-wave-modulation method with a wide gain range can greatly reduce the insulation design difficulty of the intermediate AC side high-frequency transformer and the voltage stress on the AC side. Case 3 demonstrates the extended-phase-shift (EPS) control of three-port DC-DC converter. Combining the voltage sorting algorithm of voltage sequencing and cyclic switching, a strategy of voltage equalization for grouped capacitors is proposed. Considering the various application scenarios of actual working conditions, the soft switching characteristics and multi-port power characteristics of the DC transformer are analyzed. In order to verify the feasibility of the DC transformer structure and its control strategy, a simulation model was built in Matlab/Simulink and the results were verified. The results are in accordance with the theoretical analysis.

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