OPTIMAL TRANSMISSION SWITCHING

Abstract

Transmission systems have 'been modeled as a fixed topology for finding the operating policies of a power system. In this report a method is described to find optimal topology of the transmission network so that the dispatch cost is minimized. Optimal topology of a transmission network can be determined by controlling- the transmission line circuit breaker in addition to control generator output to meet the demand efficiently. Mathematical model is formulated by representing transmission line switching as binary variable and power flow in the lines and generation by continuous variable. Hence the formulated optimization problem is a mixed integer linear programming problem. The constraints considered in the problem formulae are the linear load flow equations, upper and lower bounds on bus voltage phase angles, upper and lower bounds on real power generated by each generator, upper and lower bounds on real power flow through each lines and limitation on number of transmission lines opening allowed. One impediment to the use of Optimal. Transmission Switching (OTS) in practice is the very long computing time to solve it. This report proposes a heuristics which rely on a line-ranking. parameter that is based on the optimal solution to the ordinary dc optimal power flow problem, a linear program. Python programming language is used to solve the problem. The problem is solved by using GLPK solver. GLPK solver use cutting plain method to solve the optimization problem.The proposed methods are tested on IEEE 30-bus and IEEE 118-bus systems, and compare results between Seq-LP heuristic and with the most common previous methods in the literature, which solves a sequence of MIPs, removing one line at. a time, with each MIP having all binary variables, i.e., one for each line. This heuristics is much faster than the previous method from the literature. In almost all cases tested, the proposed heuristics find cost reductions that are approximately as large as the previous method. The computing time reductions by Seq-LP method are so great that OTS may now be practical with respect to the computational time . issue. The effect of transmission switching under. restructured power system environment is also considered and better results are obtained.