Incorporating unified interphase power controllers into robust multi-period transmission expansion planning to mitigate short-circuit level

Abstract

With continuously increasing power demands, installed generation capacity and scale of the transmission grid, suppressing the short-circuit level is an inevitable necessity. In this paper, the authors present a new robust multi-period model developed for transmission expansion planning (TEP) in the presence of unified interphase power controllers (UIPCs) to mitigate the short-circuit level. UIPCs represent one of the promising short-circuit-level suppressing FACTS devices that could flexibly and reliably maintain their desirable performance under both normal and fault conditions. The proposed planning model is outlined using a bi-level optimization problem. The TEP objectives, modeled through the upper-level problem, are the minimization of the investment and congestion costs, while satisfying long- and short-term constraints over the planning horizon. In this problem, a potent information-gap decision theory was also employed to tackle the risks of planning that stem from severe uncertainties in predicted demand and estimated capital expenditure budget. The lower-level problem, however, acts as a central core of the upper-level problem, and its target is the maximization of the community welfare function under both normal and fault conditions. To solve the proposed large-scale mixed-integer nonlinear bi-level model, a powerful symphony orchestra search algorithm was used. The proposed planning methodology was applied to the modified 400-kV 52-bus Iranian power grid and IEEE 138/230-kV 24-bus reliability test system; its sufficiency and profitableness will be demonstrated by exhaustive case studies.