  The Variable Series Reactors (VSRs) can efficiently control the power flow
through the adjustment of the line reactance. When they are appropriately
allocated in the power network, the transmission congestion and generation cost
can be reduced. This paper proposes a planning model to optimally allocate VSRs
considering AC constraints and multi-scenarios including base case and
contingencies. The planning model is originally a non-convex large scale mixed
integer nonlinear program (MINLP), which is generally intractable. The proposed
Benders approach decomposes the MINLP model into a mixed integer linear program
(MILP) master problem and a number of nonlinear subproblems. Numerical case
studies based on IEEE 118-bus demonstrate the high performance of the proposed
approach.
