Reconfiguration of distribution systems for stability margin enhancement using tabu search

The reconfiguration of distribution systems is usually done to minimize real power losses, or to balance the load among feeders. Many reconfiguration methods based on heuristics, optimization, different kinds of artificial intelligence, and evolutive programming can be found in the literature. Similarly to transmission systems, distribution systems are also likely to experience voltage instability problems, especially during load peak hours in predominantly industrial areas. In this paper a reconfiguration algorithm based on tabu search for maximizing the security margin to voltage collapse (or loading margin) is proposed. Tabu search is a technique that consists basically of generating a number of appropriate possible configurations and choosing those that present desired characteristics as far as the objective to be attained is concerned. The evaluation of the different configurations is done with the help of voltage stability indices. In particular, an index that can be obtained with very small computational effort yet provides important information about the systems´ stability condition was chosen. Simulation tests were conducted with small test to large realistic systems. The results have shown that the proposed method is very efficient and system configurations with the maximum loading margins and near-minimum real power losses are obtained, A comparison between adopting real power losses minimization and loading margin maximization is done. Moreover, a procedure for switching between those two objectives as a function of the total load daily curve is proposed.