Abstract—This paper simulates transient situations of a uni-grounded low-voltage (LV) AC microgrid through various fault tests and operation transition tests between grid-connected and islanded modes of the uni-grounded microgrid. Based on transient simulation results, available fault protection methods are proposed for main and back-up protection of a uni-grounded AC microgrid. As a result, main contributions of the paper are: (i) analysing transient responses of a uni-grounded LVAC microgrid through line-to-line faults, line-to-ground faults, three-phase fault and microgrid operation transition tests; and (ii) proposing available fault protection methods for uni-grounded microgrids, such as: non-directional or directional overcurrent protection, under/over voltage protection, differential protection, voltage-restrained overcurrent protection, and other protection principles not based on phase currents and voltages (e.g. total harmonic distortion detection of currents and voltages, using sequence components of current and voltage, 3I0 or 3V0 components).

Index Terms—Fault protection, microgrid transient responses, microgrid simulation, uni-grounded microgrid.

Keng-Yu Lien is with the Department of Avionics, China University of Science and Technology, Hsinchu, Taiwan.
Duong Minh Bui and Ching-Chih Lin are with the Department of Electrical Engineering, Chung Yuan Christian University, Chungli, Taiwan.
Yung-Ruei Chang, Yih-Der Lee, and Jheng-Lun Jiang are with the Institute of Nuclear Energy Research, Atomic Energy Council, Taoyuan, Taiwan.

Cite:Keng-Yu Lien, Duong Minh Bui, Yung-Ruei Chang, Yih-Der Lee, Jheng-Lun Jiang, Ching-Chih Lin, "Transient Responses and Appropriate Fault Protection Solutions of Uni-grounded AC Microgrids," International Journal of Computer and Electrical Engineering vol. 8, no. 2, pp. 132-150, 2016.