Fault Ride-Through Enhancement of Grid-Connected DC Microgrids Using SFCL

The fault current levels of DC microgrids are extremely high. For faults on the grid side, these high levels can cause fast tripping, thereby hindering the fault ride-through capability of the DC microgrid. Accordingly, this paper aims to use superconducting fault current limiter (SFCL) to limit fault current contribution from microgrid components to the grid side and enhance fault ride-through capability. The considered DC microgrid in the present study has a common DC bus with a bipolar structure. Photovoltaic (PV) arrays, wind energy systems, and Li-ion batteries are connected centrally to the DC bus. Two identical SFCL units were inserted between the DC bus and the main grid on the positive and negative poles. The microgrid performance under grid faults was investigated for different types of faults. The fault currents contributed by various microgrid components were analyzed without and with using SFCL. Also, the state of charge and rate of current rising for batteries were evaluated. SFCL succeeded in limiting the fault currents effectively and keeping safe operation for the microgrid components.