A dynamic programming-based heuristic approach for optimal transmission switching problem with N-1 reliability criterion

Minimization of operating costs is one of the most important objectives of power system operators. To achieve this goal, several optimization problems such as unit commitment and optimal power flow have been introduced. Historically, in these problems, the transmission network has been considered as a static system, i.e., the ability of transmission lines switching is not modeled. On the other hand, it has been shown that transmission line switching can significantly reduce operating costs by the means of topology modification. However, considering this capability, a large number of binary variables are introduced in the objective function, and as a consequence, the computation time will be considerably increased. To address this problem, this paper tries to propose an effective method based on the dynamic programming algorithm for solving the optimal transmission switching (OTS). In this method, firstly the OTS is modeled as a step by step problem. Then, in order to reduce the computation time, in each step, some lines are chosen as candidates for outage by using appropriate criteria. The proposed method not only reduces the computation time but also considers the effects of transmission switching on the operational constraints that have not been modeled in the previous DC models. It is also shown that the method can effectively consider the N-1 security criterion. Finally, in order to illustrate the effectiveness of the proposed method, it is applied to the IEEE 118-Bus test system and the results are discussed.