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 large number of thermal-limit constraints, the authors 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 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. They have used the DT method embedded with these two new techniques in solving numerous OPFs with 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 large number of thermal-limit constraints.