Multi-area control of overlapping areas in power systems for FACTS control

As power systems generally are large interconnected systems controlled by several parties, centralized optimal power flow (OPF) control taking the entire grid into account is often not feasible. To use optimal control in power systems nevertheless, the overall system is decomposed into areas with associated subproblems, which are solved in an iterative way. Currently available decomposition techniques assume that the models and control objectives of areas are formulated to be non-overlapping, i.e., the border of one area is at the same time also the border of a neighboring area. However, when the areas are determined independently from each other, e.g., by sensitivity analysis, the areas can be overlapping, making currently existing techniques not directly applicable. In this paper, we extend one of these techniques, viz. a modified Lagrange decomposition method, to the case of overlapping areas. Simulations are carried out on an adjusted IEEE 57-bus system in which the controlled entities are FACTS devices and the objective is to improve system security.