Dynamic Impact of Microgrids on Power Systems
Environmental and technical merits of Microgrids (MGs), as clusters of Distributed Energy Resources (DERs), make them attractive to fulfill the increasing needs for electrical energy. While low penetration of MGs/DERs has little influence on host grid stability and dynamics, the ability of the system to accommodate high penetration of MGs is in concern. As MGs penetration level increases, conventional generators, along with the inherent rotational inertia property they contribute will be displaced by Distributed Generations (DGs). While conventional generator rotating mass, i.e., rotational inertia, significantly contribute to power system stability and dynamics via providing kinetic energy to the grid (or absorb it from the grid) in case of frequency deviation, a MG has small or no rotational inertia. Thus, loss or reduction of rotational inertia in response to increasing MGs penetration level leads to slow reaction of traditional frequency schemes to disturbances, which, in turn, may result in large deviations and probable instability. Therefore, one of the impediments to increase MGs penetration level stems from the reduction of system inertia which, in turn, renders dynamics faster.