Load sharing of autonomous distribution-level microgrids

This paper investigates the problem of appropriate load sharing in an autonomous distribution-level microgrid, where the considerable resistive component of the line impedance makes the conventional frequency and voltage droop controls impractical. To improve active and reactive power sharing, a power control strategy is proposed which contains a virtual inductor at the interfacing inverter output and a supplementary control loop around the conventional droop control of each DG converter. Specifically, the virtual inductance prevents the coupling between the real and reactive power control by introducing a predominantly inductive impedance, and the supplementary control loop stabilizes the system while using high droop gains which are needed for proper load sharing. The proposed control strategy is proven to ensure satisfactory load sharing while stabilizing the system for a range of operating conditions.