Impedance Severity Index Based Hybrid Islanding Detection Approach for Zonal DC Microgrids

A significant obstacle to the greater integration of renewable energy sources is the absence of an efficient protection system. Unintentional islanding can cause system instability and pose a threat to the safety of workers. However, DC microgrid islanding detection schemes have not been rigorously addressed in the literature yet. In order to overcome the above-mentioned issues, this research proposes a two stage hybrid islanding detection approach (IDA) for DC microgrids (DC MGs) to address the significant non detection zone (NDZ) and power quality degradation of prior IDAs. Using the proposed impedance emergency severity index (
$ESI_{z}$
) based hybrid IDA, a disturbance is first recognized by calculating the magnitude of
$ESI_{z}$
. In order to distinguish between islanding and other disruptions, an under over voltage (UOV) based current perturbation is then placed on top of the current. The proposed approach makes use of local measurement parameters of the distributed generation (DG) units. It does not impact the power quality while operating normally and has a nearly zero NDZ. On a 750 V zonal DC MG test system, numerous case studies are performed to demonstrate the nerformance of the proposed hybrid IDA.