A Novel Passive Technique Based on Superimposed Negative Sequence Impedance to Detect Islanding in AC Microgrids

Improper detection of islanding in a microgrid can lead to power quality issues, reclosing failures, and serious equipment damage, and it also poses a threat to security personnel. Therefore, the detection of islanding is a critical task for ensuring the proper functioning of the microgrid system. In this article, an effective islanding detection method is presented for detecting islanding in the modern distribution test system. The proposed islanding scheme employs the concept of superimposed negative sequence impedance to derive the islanding event index (IEI). Unlike many schemes available, this scheme does not degrade the power quality and provides a large difference in IEIs during islanding and non-islanding events. It properly distinguishes between islanding and non-islanding events at zero power mismatch. All the simulations have been carried out in the MATLAB/Simulink environment. Additionally, this technique has also been validated on the OPL-RT real-time simulator. The results showed the superiority of this method over several previous methods and detected islanding in 66 msec - with a large gap of the order of 104 in IEIs during islanding and non-islanding events - making this method more accurate and robust. Moreover, the scheme can be implemented into any existing system simply and inexpensively.