A Novel Dual-Switch Capacitor Series DC Transformer Topology with Faults and Inrush Current Suppression

DC transformer is important interface between multi terminal flexible DC distribution networks, DC loads, and DC microgrids. This paper proposes a topology structure of a dual switched capacitor series DC transformer suitable for multi terminal flexible DC distribution networks. When a short circuit fault occurs on the medium voltage DC side, the dual switched capacitor series module is locked to block the external discharge of the capacitor, quickly cut off the fault, and restore operation quickly. When the instantaneous blocking of communication faults causes a step like fluctuation in the power flow of each port, the power flow is prone to flow into the DC transformer with low impedance, triggering the protection shutdown. At this time, the dual switch capacitor series module blocking is used to prevent external surge and improve the reliability of the system. Compared to the conventional full-bridge + DAB topology, the proposed topology eliminates two switching tubes. Additionally, it offers advantages such as fault current suppression, inrush current suppression, higher efficiency, and reduced economic costs. Finally, the simulation and actual large-scale engineering test results verified the effectiveness and practicality of the proposed method, which has practical value in engineering.