The invention discloses a three-stage AC optimal
transmission switching method based on a relaxation model, and the method comprises the following steps: 1, screening a breakable
branch through solving an optimal solution of the relaxation model in a first stage, and reducing the scale of a
system; 2, in the second stage, sorting is carried out by solving the optimal solution of the alternating-current optimal
power flow of disconnection of a single
branch; and step 3, in the third stage, solving by adopting a
branch and bound method according to the sorting sequence of the second stage, and finally determining an optimal solution of
alternating current optimal
transmission switching and a branch on-off scheme. According to the method, the dimensionality of the optimal
transmission switching problem is effectively reduced, and the calculation efficiency and speed are improved; an
alternating current optimal transmission switching relaxation problem is solved by adopting a method based on a quotient
gradient system and IPOPT, so that the calculation convergence and speed are guaranteed, and the
algorithm robustness is improved;
branch and bound calculation is carried out according to the
alternating current optimal
power flow solution sorting result sequence of the
cut-off single branch, and it is guaranteed that a high-quality line
cut-off scheme is obtained through solving; in the calculation process, island branch
processing is considered, the island phenomenon in the topology change process is prevented, and
power grid splitting and unnecessary load outage are effectively avoided.