Microgrids are an emerging alternative as an energy backup system for critical electric loads and have improved performance compared to the traditional architecture where a single emergency diesel generator is tied to an individual building. Both architectures are dependent on the reliability of their individual generators and a quantitative and realistic comparison of the overall system reliability of the two architectures is lacking. Using recently published work on emergency diesel generator finite reliability, a quantitative methodology is presented to compare the reliability of a microgrid architecture based on centralized emergency diesel generators to the traditional approach of generators tied to individual buildings. Three system reliability performance metrics are calculated as a function of outage duration: (1) probability to meet 100% of the critical load; (2) expected fraction of lost load; and (3) probability to meet the highest priority critical loads. It is shown that stand-alone building-tied emergency diesel generators systems, even when two emergency diesel generators are used per building, cannot provide the reliability required to sustain critical loads for a grid outage lasting multiple days. Due to their network configuration and ability to share load, diesel generator-based microgrid configurations are estimated to have ≥ 93% probability of powering all buildings for a 2-week outage there the individual building-tied emergency diesel generator architecture has a ≤20% probability. Microgrids do present other susceptibilities that are site specific and should be considered including vulnerabilities associated with the on-campus distribution system and cybersecurity.

微电网是新兴的替代方案，可作为关键电力负载的能源备份系统，与传统架构相比，微电网具有更高的性能，在传统架构中，单个应急柴油发电机束缚在单个建筑物上。两种架构都依赖于其各自的生成器的可靠性，并且缺乏两种架构的整体系统可靠性的定量和现实比较。利用最近发表的关于应急柴油发电机有限可靠性的工作，提出了一种定量方法，用于比较基于集中式应急柴油发电机的微电网架构的可靠性与与单个建筑物捆绑的传统发电机的可靠性。根据中断持续时间来计算三个系统可靠性性能指标：（1）达到100％临界负荷的概率；（2）预期的空载分数；（3）满足最高优先级临界负载的概率。结果表明，即使在每个建筑物中使用两台应急柴油发电机，独立的，与建筑物捆绑的应急柴油发电机系统也无法提供维持关键负载以维持多天电网中断所需的可靠性。由于其网络配置和分担负载的能力，基于柴油发电机的微电网配置估计有≥93％的概率在两周内为所有建筑物供电，而与建筑物相连的应急柴油发电机架构的≤20％可能性。