Microgrid (MG), as a cluster of Distributed Generations (DGs) and local loads, may be characterized with zero or small inertia constant. Reduction of system rotational inertia, in response to increasing MGs penetration level, renders frequency dynamics faster. This paper presents an attempt to propose a new analytical approach to mathematically assess the impact of MGs penetration level on power system frequency stability. In this way, an experimental-based model is employed to make the simulation results realistic. The method interprets the frequency dynamic behavior of the penetrated system based on the conventional system in terms of frequency nadir, steady state deviation and a 15-second rolling window.
