Virtual DC machine based islanding detection method in DC distribution system and stability enhancement

DC distribution system has become a hot spot in the field of integration of distributed generators (DGs) and DC loads owing to the improved system reliability and efficiency. Virtual DC machine (VDCM) control provides DC-DC converters inertia feature and improves stability. Meanwhile, islanding detection has become the key issue of the reliable operation of DC distribution system but relative researches are still in infancy. This paper presents a VDCM based islanding detection method for DGs using voltage feedback. The feedback gain that causes system instability in islanding condition while still preserves stability in grid-connected mode is theoretically obtained. To improve the system stability and extend the feedback gain range to realize a better islanding detection performance, an active damping control for stability enhancement is further proposed. The impact of system parameters on stability is analyzed in detail. Both the proposed islanding detection method and stability enhancement for DGs are verified by system simulation.