A Novel DC-DC Multi-Level Converter for Interfacing an SST and a Bipolar DC Grid

The pioneering models of future power grids are driving the implementation of innovative power electronics technologies aimed at power management. In this revolutionary framework, the applicability and architecture of a novel DC-DC multi-level converter (MLC) interfacing a solid-state transformer (SST) and forming a hybrid bipolar DC grid is proposed in this paper. The proposed DC-DC MLC has as worthy features three individual inputs and a single output, establishing a bipolar DC voltage output, as well as the ability of functioning with three voltage levels, allowing the reduction of the voltage stress in the semiconductors. The applicability and architecture of the proposed DC-DC MLC, interfacing the secondary side of a solid-state transformer (SST), and establishing the bipolar DC grid, is presented. Concerning control flexibility, as underlying commitment, the proposed DC-DC MLC operates with balanced voltages for ensuring the correct operation of the bipolar DC grid, while permitting to control the input currents as function of the operating power, i.e., ensuring a balanced power on the three interfaces of the SST secondary side. The main computational results validate the proposed DC-DC MLC for various operating requirements, revealing its important features and applicability for interfacing an SST and forming a bipolar DC grid.