Coordinated Optimal Dispatch of Energy Storage in a Network of Grid-Connected Microgrids

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A method is proposed for coordinated optimal dispatch of storage units in a group of grid-connected microgrids with storage and renewable energy assets to minimize the electricity costs. The method allows the microgrids to share these resources and collectively interact with the grid as one customer. A multiobjective optimization problem is formulated to obtain optimal storage charge/discharge activities using a forecast of the microgrids net electricity demands within a rolling horizon control framework. The solution to this problem also produces a virtual decomposition of the microgrids net power into local and grid components for the purpose of computing their share of electricity cost. The multiple-objective optimization is converted to a single-objective optimization by adding up the costs of the individual microgrids. An equivalent linear program free of binary/integer variables is derived from the original nonlinear optimization model, which can be effectively solved using existing solvers. Results of numerical simulations with real demand and renewable generation data are presented. They demonstrate that the coordinated optimal dispatch of the energy storage devices with the possibility of local energy transactions can significantly reduce the microgrids electricity costs compared to the cases in which they interact with the utility grid on an individual basis.