Control Scheme for Autonomous and Smooth Mode Switching of Bidirectional DC–DC Converters in a DC Microgrid

In dc microgrid (MG) systems, energy storage systems (ESSs) capable of short- or long-term energy buffering are indispensable for energy management and providing high-quality electric energy. The MG should be able to operate in both islanded and grid-connected modes. A sudden failure of ac utility grids can lead to an inoperable condition of the MG or a large transient phenomenon accompanied by oscillation and overshoot during the mode transition. This paper proposes a control scheme of the bidirectional dc-dc converter for the ESS to resolve the issue associated with mode switching. The proposed control scheme provides autonomous and smooth mode switching, thereby reducing the reliance on the communication with the central controller, and enhancing the reliability of the system. To validate the proposed concept, simulation results and experimental results are provided.