Quantifying Microgrid Resilience by Determining Survivable Durations of Random Outages

Resilience is increasingly important in microgrid design as extreme weather and grid disturbances become more frequent, yet there is no widely accepted, operationally interpretable metric for microgrids. This paper defines a planning-oriented resilience metric—the mean survivable outage duration, i.e., the average number of hours a microgrid can sustain critical load during islanded operation under outages initiated at each hour of a representative year. We contribute: (i) a transparent simulation workflow that couples NREL’s REopt dispatch with an open-source Excel/VBA calculator to compute survivable outage duration without relying on historical outage data; and (ii) a sensitivity framework that maps resilience across solar PV and battery energy storage (BESS) capacities to quantify how distributed energy resource (DER) sizing affects sustained islanded operation. In a microgrid test case, resilience is highly sensitive to DER sizing: with PV fixed at the REopt nominal size, reducing BESS capacity by 10–50% lowers mean resilience by 7.4–94.1%; with BESS fixed at nominal, reducing PV by 10–50% lowers resilience by 6.2–87.1%. Conversely, increasing PV capacity by 50% raises mean resilience by 148.5%, compared with a 112.4% increase from a 50% BESS increase. These results show that the proposed metric and tool provide direct, decision-relevant guidance for DER sizing to enhance sustained islanded operation.