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Comprehensive reliability modeling of grid-tied microgrids using Fault Tree Analysis

Fault tree analysis (FTA) is a top-down reliability evaluation method based on Boolean logic and is used to identify the potential causes of system failures (top event) that would possibly occur due to various combinations of component failures (basic events). In this paper, FTA is used to study the reliability performance of a microgrid in grid-tied mode with photovoltaics (PV), wind turbines (WT), and battery energy storage systems (BESS) as distributed generators. Three FTA analyses are performed for three cases, namely microgrid (MG) in islanded mode, utility grid (UG), and finally MG in grid-tied mode (UG + MG). Failure rate and repair rate data for the analyses are drawn from several public databases, reports, and literature. Quantitative and qualitative assessments of the FTA results and performance measures such as unavailability, conditional failure intensity, failure frequency, and the number of failures are presented. Furthermore, to provide a more comprehensive and thorough understanding of the system reliability, several other essential performance measures such as marginality, criticality, diagnostic, risk achievement, and risk reduction for each basic event and gate are also calculated and presented. Cut sets of the top failure events are also documented. Results prove the feasibility and effectiveness of the proposed method.