A DC-Current-Bus-Coupled Multi-Port Power Electronic Transformer and Its Control Strategy

High power density and decoupled control of port power are important but generally difficult to be achieved at the same time for multi-port power electronic transformers (MP-PETs). This paper proposes a new MP-PET consisting of a common DC current bus, a grid-connected current-source converter (CSC) and several hybrid dual-active-bridges (H-DABs). The soft switching modulation method of the H-DABs is presented for different power flow directions, and the transmission power range is analyzed. The control methods of the different parts of the MP-PET are also proposed. The new MP-PET with the proposed control strategy requires fewer large capacitors and achieves flexible decoupling of the power control for each port. Simulation is carried out for the new MP-PET in an energy-storage system with multiple batteries. The simulation results verify the effectiveness of the proposed topology and its control method.