An integrated adequacy and stability assessment approach for microgrid reliability analysis under inverter-based resource contingency.

Power system reliability evaluation has been conducted based on steady-state analysis approaches such as optimal power flow calculations with minimum load curtailments. These approaches assume that a power system would return to a stable operating state after a contingency (faults, short circuits, etc.), i.e., power system dynamics are not considered. Although this assumption has been widely accepted for conventional power systems, microgrids are more vulnerable to large disturbances than conventional power systems are. In other words, the likelihood of an unstable transition from pre-event to post-event conditions is higher in the case of microgrids than in the case of conventional power grids. Therefore, it has become important to consider both generation adequacy and transient stability in microgrid reliability evaluation. This paper develops an integrated transient stability and reliability assessment approach for microgrids to capture both inadequacy and instability conditions. A Lyapunov function-based approach is developed to determine the stability region for each contingency in calculating the reliability indices. Also, a linearized AC optimal power flow model is developed for composite system reliability evaluation. This paper also provides a set of indices to quantify the impact of transient instability on the reliability of microgrids. The proposed approach is applied to the IEEE 33-bus system in the islanded mode using sedumi and YALMIP optimizers in MATLAB. The results show that 29.19% of the contingencies for which the microgrid is deemed reliable based on steady-state analyses causes unstable conditions, which justifies the need for integrating steady-state and transient conditions in microgrid reliability evaluation. • Integrated framework for microgrid reliability and transient stability assessment. • New transient energy function for large-scale microgrid stability assessment. • Introduced stability-reliability indices for microgrid analysis. [ABSTRACT FROM AUTHOR]