A novel control scheme for microgrid inverters seamless transferring between grid-connected and islanding mode

Microgrid (MG) system in integration with the utility grid is a revolutionizing way of reliable supply to critical loads during utility shutdown or outage. The inverter in this system, responsible for energy interchange between MG and utility grid, has vital importance. A seamless transferring between this inverters' operating modes (grid-connected (GC) and Islanding modes) is a key to the stable system operation. This paper represents a novel control scheme contingent on indirect current control for seamless transferring between these operating modes. Moreover, a proportional integral based software phase-lock loop (PLL) is adopted for synchronization purpose to ensure precise phase lock during mode-switching. Finally, a digital control based experimental prototype of this inverter is designed and built according to the MG requirements to authenticate the proposed control scheme.