Operation challenges of feeder shunt capacitors in islanded microgrids

Active distribution systems are moving towards a new paradigm shift, where they can be clustered into microgrids capable of operating in both grid-tied and islanded modes depending on the penetration levels and types of the distributed generation (DG) units. Previous studies put on view lots of advantages and concerns for microgrids operation in islanded mode, whether it is initiated for emergency, intentionally planned or permanent island system purposes. One of the concerns that have not been addressed yet, is the functionality of the existing feeders shunt capacitors (FSCs) when microgrids operate in islanded mode. Hence, this paper investigates the operation conflicts between DG units and FSCs during the islanded microgrid mode of operation. These operation conflicts have been validated through conducting simulations for different local control schemes of FSCs. The results show that major voltage regulation and reactive power control problems might arise when DG units are droop-controlled and FSCs utilize conventional control schemes. Further, a new local control scheme for FSCs has been proposed to mitigate their operational challenges in islanded microgrids.