Preservation of overcurrent relays coordination in microgrids by application of static series compensators

In this paper, the application of static series compensator as a fault current limiter is proposed to preserve the integrity of the overcurrent relays´ settings in a microgrid for both modes of operations, i.e., utility-grid connected and autonomous (islanded). Static series compensator could be multiple low-power single-phase inverters that attach to the overhead conductor and dynamically control the line impedance or with the same architecture could control the impedance of the underground cables. The static series compensator would effectively increase the line impedance during faults in order to alleviate the contribution of fault current from the utility-grid, so the fault current does not change appreciably in gird-connected or autonomous modes. The static series compensators are controlled by using customary communication techniques.