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TitleSynthetic harmonic distance relaying for inverter-based islanded microgrids
AuthorSaleh, K A; Allam, M AORCID logo
SourceIEEE Power and Energy Magazine vol. 8, 2021 p. 258-267, Open Access logo Open Access
Alt SeriesNatural Resources Canada, Contribution Series 20210534
Mediapaper; on-line; digital
File formatpdf
Subjectsengineering geology; Science and Technology
Illustrationsschematic representations; graphs; tables; distribution diagrams
ProgramCanmetENERGY - Varennes Net Zero Solar Building
Released2021 06 14
AbstractFaults in inverter-based islanded microgrids can be a formidable protection challenge due to (i) low fault current magnitudes, (ii) compromised fault current phase angles, and (iii) bidirectional \'1dow of fault currents. This paper proposes a protection scheme that disregards the fault signals altogether. Instead, it relies on decoupled synthesized signals introduced only during fault conditions. This scheme is achieved by exploiting the existing inverter-based distributed generation (IBDG) controllers to inject synthetic harmonic voltages and currents. These synthetic signals are measured locally by digital relays in the microgrid to develop a novel synthetic harmonic distance relay (SHDR). Apart from the utilization of high-order harmonic signals that enhance SHDR reactance reach, further reach improvement is achieved via the introduction of line reactance magni\'1cers (LRMs). Transient studies in PSCAD/EMTDC verify the performance of the proposed scheme under various faults, contingencies, and different microgrid con\'1cgurations.
Summary(Plain Language Summary, not published)
The concept of "microgrids" has become increasingly important as a viable solution to integrate distributed small-scale renewable energy sources and energy storage systems into electrical networks. One key advantage of these microgrids is their ability to operate independently from utilities in "islanded" mode, in which they primarily rely on local distributed generators (DGs) for power. However, protection of islanded microgrids becomes a major challenge, since conventional protection schemes fail in such systems because DGs exhibit fault behaviours different from traditional energy sources. Accordingly, this research proposes a new protection scheme that exploits the existing DGs to identify faults. The proposed scheme modifies the DGs' controllers, such that they inject unique signals to the electrical network upon fault detection. In addition, to identify the fault location accurately, the scheme integrates additional circuit elements to the microgrid, which are only activated during faults. Finally, a protection relay is introduced to detect faults and to identify the fault location by measuring and processing the unique signals injected by the DGs. Simulations have proved the proposed scheme effective under various faults, contingencies, and different microgrid configurations.

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