Formulation and solution method on flexible transmission expansion planning

In this paper, a transmission expansion planning formulation is proposed that simultaneously considers investment in phase shifters and in primary network assets, such as lines and transformers. Based on the classical network expansion planning formulation, a new mixed-integer linear programming (MILP) formulation is built to deal with the placement of phase shifter along with adding new branches, while the N-1 security criterion is considered. The curtailment of wind farm output is also discussed. The whole problem is solved by Benders' decomposition method. Simulations have been done on the Garver 6-bus system. The planning schemes obtained from the proposed method showing cost reduction offered by phase shifters over the traditional circuit expansion.