  With the integration of Renewable Energy Sources (RESs), the power network
must be robust to handle the system's uncertain scenarios. DC Transmission
Expansion Planning (TEP) plans are generally not feasible for the AC network. A
first bi-level Robust Optimization (RO) solution approach for AC TEP with
injection uncertainties in loads and RESs generations is proposed in this
paper. It utilizes a well-known convex relaxation and is solved by Benders
Decomposition (BD), where the master determines the robust AC TEP plan. A novel
dual slave model is developed for the second level of BD, which circumvents the
issues in using the Conic Duality Theory (CDT), and aids in the worst-case
realization of uncertainties using a novel set of constraints. The developed
dual slave is not a mixed-integer problem and is solved using the Primal-Dual
Interior Point Method (PDIPM). The proposed work also uses additional linear
constraints to reduce BD's computational burden and direct the master towards
optimality. Monte-Carlo Simulation (MCS) based verification, via actual
nonlinear and non-convex AC Optimal Power Flow (OPF), proves 100% robustness of
the TEP plans for all scenarios.
