Determination of storage required to meet reliability guarantees on island-capable microgrids with intermittent sources

It is well known that the presence of energy storage ameliorates the reliability challenges posed by intermittent sources. However, a quantitative assessment of the exact amount of storage required to meet a reliability target or guarantee in the presence of intermittent sources is not trivial. This paper describes a practical approach to achieving this. First, an analytical approach is developed for determining the amount of storage required to meet a reliability target at a specific load point. Then the method is extended to a more complex island-capable microgrid system where initial reliability assessment and final verification of reliability guarantee are performed using sequential Monte Carlo simulation. The necessary component and system models are developed and described, and a mock military base is used to demonstrate the method. The work reported was performed under a contract from Sandia National Laboratory to determine storage need in order to provide reliability guarantee on an island-capable military microgrid, but the approach applies as well to civilian systems, both islanded and grid-connected. A method for determining an optimal storage mix is also developed.