Reliability Evaluation of Islanded Microgrids with Stochastic Distributed Generation

Microgrids can potentially improve distribution system reliability when enabled to operate in an islanded mode. Future microgrids will likely contain substantial amounts of stochastic generation, which have a more uncertain impact on reliability as compared to dispatchable generation sources. New methods that realistically represent the stochastic behavior of these sources and their impact on reliability need to be developed. This paper proposes a new methodology for assessing local generation adequacy for an islanded microgrid with limited stochastic resources. Instead of modeling the generation and load independently, a combined generation-to-load ratio (GLR) is modeled as a Markov process, thereby preserving the correlation among disperse photovoltaic installations and the load. Historical data on solar irradiation and electric load are scaled and smoothed to account for their spatial distribution and used to estimate the Markov transition rates and the final reliability indices. The process illustrates the impact of stochastic behavior on reliability in a transparent manner and is useful for evaluating the reliability benefits of load curtailment and increasing local generation capacity.