Operations- and uncertainty-aware installation of FACTS devices in a large transmission system

Decentralized electricity markets and greater integration of renewables demand expansion of the existing transmission infrastructure to accommodate inflected variabilities in power flows. However, such expansion is severely limited in many countries because of political and environmental issues. Furthermore, high renewables integration requires additional reactive power support, which forces the transmission system operators to utilize the existing grid creatively, for example, take advantage of new technologies, such as flexible alternating current transmission system (FACTS) devices. We formulate, analyze, and solve the challenging investment planning problem of installation in existing large-scale transmission grid multiple FACTS devices of two types (series capacitors and static var compensators). We account for details of the ac character of power flows, probabilistic modeling of multiple load scenarios, FACTS devices flexibility in terms of their adjustments within the capacity constraints, and long-term practical tradeoffs between capital versus operational expenditures. It is demonstrated that proper installation of the devices allows to do both - extend or improve the feasibility domain for the system and decrease long-term power generation cost (make cheaper generation available). Nonlinear, nonconvex, and multiple-scenario-aware optimization is resolved through an efficient heuristic algorithm consisting of a sequence of quadratic programmings solved by CPLEX combined with exact ac power flow resolution for each scenario for maintaining feasible operational states during iterations. Efficiency and scalability of the approach are illustrated on the IEEE 30-bus model and the 2736-bus Polish model from Matpower.