Power and control characteristics of an isolated three-port DC-DC converter under DCM operations

Isolated multiport DC-DC converters offer an efficient solution to meet the increasing demand of integrating energy delivery elements (EDEs) of various type like renewable energy sources (RESs), energy storage devices (ESDs) and mains. This paper deals with an isolated three-port DC-DC converter (3PC): two ports are connected to EDEs, respectively to a RES and an ESD, and a port is connected to the load. The 3PC characteristics in terms of power capabilities and control laws are investigated for two discontinuous conduction mode (DCM) operations and two operational working situations. The DCM operations are i) full DCM (FDCM), with all the ports operating in DCM, and ii) mixed discontinuous conduction mode, with the ESD-connected port operating in DCM and the other ports in continuous conduction mode. The working situations are i) both EDEs deliver power to the load, and ii) RES delivers power to ESD and the load. The theoretical findings are explicated by waveforms and diagrams.