A Novel technique for Power sharing and Synchronization of Distributed Generators in an Islanded AC Microgrid

Popularly, the VSIs of the decentralized, islanded microgrids, use the voltage and frequency droop laws for proportional power sharing. These cause the output voltage amplitude and frequency of the VSIs to deviate from their nominal values. Because of the decentralized architecture of the microgrid, any incoming DG unit(IDG) will be unaware of these deviations. In this situation, this DG unit will initially generate an output voltage whose amplitude and frequency are at their respective nominal values. The difference in output voltage amplitude and frequency will cause a high and undesirable current to flow between the generators. In this paper, this problem is solved by introducing a novel synchronization scheme. The scheme makes any incoming DG unit operate first in the Intermediate mode and then in the Droop controlled mode. These modes are designed to meet the IEEE 1547-2003 std and make the synchronization possible for the incoming DG unit.