Improvements on the Duality-Based Method Used in Solving Optimal Power Flow Problems

To improve the previously developed dual-type (DT) method used in solving optimal power flow (OPF) problems with a large number of thermal-limit constraints, we propose two new techniques in this paper. The first one is a graph-method-based decomposition technique, which can decompose the large-dimension projection problem caused by the large number of thermal-limit constraints into several independent medium-dimension projection subproblems at the expense of a slight increment of the dual problem's dimension. The second technique is an active-set strategy-based DT method, which can solve the medium-dimension projection subproblems efficiently. We have used the DT method embedded with these two new techniques in solving numerous OPFs with a large number of thermal-limit constraints. The test results show that the proposed techniques are very efficient and effectively improve the DT method for handling a large number of thermal-limit constraints.