A stochastic frequency security constrained optimization model for day-ahead energy and reserve scheduling of islanded multi-microgrids systems

Small size of microgrids (MGs), low inertia, and small scale of distributed generations, and high intermittent energy delivery of renewable generations, make the frequency security an important issue in the islanded multi-microgrids (IMMG) systems which should be considered subject to the techno-economic constraints of MGs. Motivated by this need, this article proposes a two-stage stochastic optimization model for day-ahead energy and reserve scheduling of IMMG systems. The objective of the proposed model is to minimize total operation cost of IMMG while the frequency security of system is preserved within a predefined range. To this end, the hierarchical frequency structure of IMMG system including primary, secondary, and tertiary control levels are precisely formulated in mixed-integer linear programming format which can be efficiently solved by optimization software package. Meanwhile, to promote the proposed model, responsive loads and energy storage systems are considered in the energy and reserve scheduling problem. The proposed model is applied to a typical IMMG system to optimize energy and reserve scheduling over 24-hr horizon. The obtained results verify that through the proposed model, the operation costs of MGs are minimized while frequency security of the system is preserved in a cost-effective manner.