Interlinked Hybrid Microgrids with Fault Confining Capability Using a Novel MMC Topology

This paper presents a solution for the fault current elevation in interlinked hybrid microgrids. In hybrid ac-dc microgrids, the control strategy of the interlinking converter allows the distributed generators (DGs) in either microgrid to respond to any load changes in the other microgrid. This load sharing strategy result in a contribution from all DGs to the fault current in either microgrid. Therefore, a new methodology to eliminate the fault current contribution between interlinked hybrid microgrids is proposed in this work. This methodology quarantines the fault inside each microgrid and thus prevents the other microgrid from contributing to the fault current through blocking any continuous current paths. A novel Modular Multilevel Converter (MMC) topology called Modified Switched Capacitor Submodule (MSCSM) has been used to realize the fault confining strategy. A case study has been implemented to prove the effectiveness of the proposed methodology in confining the fault within its zone and preventing any inter-microgrids contribution. The results show the successful converter operation regards blocking any current contribution from the ac-microgrid when a fault occurs in the dc-microgrid thus the fault was effectively quarantined in the dc-microgrid.