Reliability as a design principle: A systematic review and integrated framework for renewable-based microgrids

Reliable operation is a central motivation for deploying renewable-based microgrids, yet reliability is frequently treated as a secondary outcome of cost-driven design rather than as a governing planning objective. Existing reviews remain fragmented across techno-economic sizing, optimization methods, and reliability assessment, limiting the translation of planning outcomes into operationally reliable systems. This paper presents a systematic rapid review that positions reliability as the central organizing principle for microgrid design. Specifically, this review systematically synthesizes recent literature to examine how planning assumptions, optimization formulations, operational flexibility mechanisms, and reliability assessment frameworks jointly shape reliability outcomes. The synthesis shows that reliability in renewable-based microgrids is governed primarily by chronological, time-coupled energy adequacy rather than installed capacity alone, with Dunkelflaute events emerging as a key determinant of adequacy failure. Reliability outcomes are shaped by the joint interaction of resource portfolios, storage operating policies, and state trajectories, network features, and protection feasibility under inverter-dominated operation. The review further demonstrates that reliability indices inherited from conventional power systems are poorly suited for renewable-based microgrids, as they compress performance into single dimensions and obscure temporal, spatial, and service-critical risk concentrations. Across optimization practice, reliability is increasingly embedded through multi-objective and constrained formulations; however, persistent gaps remain in representing correlated renewable scarcity, mission-profile-dependent component reliability, and interruption valuation (e.g., value of lost load and customer damage functions) in a consistent and decision-relevant manner. Overall, this review consolidates planning factors, optimization approaches, reliability evaluation methods, and metric suitability into an integrated roadmap for reliability-centered microgrid planning, and outlines future directions toward state-aware, service-oriented planning and assessment frameworks. • Reliability-centered framework for 100% renewable microgrid planning. • Time-coupled adequacy drives reliability under renewable energy variability. • Limitations of traditional reliability metrics are systematically analyzed. • Integrated planning framework linking design, optimization, and assessment.