Optimal Distributed Generation Placement among Interconnected Cooperative Microgrids

The significant technical and economic benefits associated with microgrids have led to vast efforts in expanding their penetration in electric power systems. The benefits, however, must be scrutinized and compared with the huge investment cost to justify future microgrid deployments. There are lots of studies about integrating distributed generation (DG) units into a single microgrid; but DG deployment in cooperative microgrids, which allows power exchange among interconnected microgrids, lacks of study. In this paper, we first study DG placement problem among interconnected cooperative microgrids. In particular, we jointly optimize the long-term DG placement and short-term system operation to minimize microgrids' total operation cost. Uncertainties, including load demands and renewable energy generation, are taken into consideration. By using Branch Flow model, the DG placement problem can be formulated as a stochastic mixed integer convex problem. We propose to solve the problem in two stages: 1) to derive the analytical expression of Optimal Power Flow (OPF) problems for the short-term operation; 2) to solve the remaining integer problem for the long-term planning. Numerical results show that an optimal DG placement can save at most 5.8 % of the long-term cost in our case studies.