On Microgrid Protection Using Synchronized Phasors

This paper proposes a reliable technique to leverage current measurements while using phasor measurement units (PMUs). The estimation of Phasors typically relies on the Discrete Fourier Transform (DFT) algorithm, to overcome its drawbacks, the Recursive-Discrete Fourier Transform (R-DFT) algorithm could be used. This study synchronizes off-nominal grid frequen-cies in phase current measurements, a common DFT analysis drawback faced in PMUs implemented in islanded microgrids, amidst voltage-based phase measurements. The proposed method uses all three-phase voltage Phasor measurements to track fun-damental frequency changes and consequently adjust all three-phase current Phasor measurements individually. This approach supports per-phase analysis for its applicability in both balanced and unbalanced conditions in microgrid operation. It offers insights into individual phase behaviors and equips the protection system to detect and mitigate symmetrical and asymmetrical disturbances. The simulation outcomes vividly show the efficacy of our method in reducing errors arising from off-nominal fundamental frequency variations. The results underscore the method's ability to differentiate between short circuit-type faults and typical tapped loads within the protection zone. This innovative approach has the potential to improve the performance of immediate microgrid protection schemes and ensure reliable operation within them. Based on our results, per-phase analysis has shown to be a more versatile and comprehensive protection strategy in scenarios where microgrids face unbalanced and asymmetrical disturbances, as opposed to a more traditional symmetrical component fault analysis because of the special nature of inverter response under abnormal conditions.