Network Reconfiguration for Loss Reduction in Three-phase Power Distribution Systems

Power distribution systems typically have tie and sectionalizing switches whose states determine the topological configuration of the network. The system configuration affects the efficiency with which the power supplied by the substation is transferred to the load. Power companies are interested in finding the most efficient configuration, the one which minimizes the real power loss of their three-phase distribution systems. In this thesis the network reconfiguration problem is formulated as single objective optimization problem with equality and inequality constraints. The proposed solution to this problem is based on a general combinatorial optimization algorithm known as simulated annealing. To ensure that a solution is feasible it must satisfy Kirchhoff’s voltage and current laws, which in a three-phase distribution system can be expressed as the threephase power flow equations. The derivation of these equations is presented along with a summary of related three-phase system modeling. The simulated annealing algorithm is described in a general context and then applied specifically to the network reconfiguration problem. Also presented here is a description of the implementation of this solution algorithm in a C language program. This program was tested on a Sun workstation, given an example system with 147 buses and 12 switches. The algorithm converged to the optimal solution in a matter of minutes demonstrating the feasibility of using simulated annealing to solve the problem of network reconfiguration for loss reduction in a three-phase power distribution system. These results provide the basis for the extension of existing methods for single-phase or balanced systems to the more complex and increasingly more necessary threephase unbalanced case.