A loss minimum re-configuration algorithm of distribution systems under three-phase unbalanced condition

Many single phase distributed generators (DGs) - such as solar cells, small scale gas-engine CHP systems, etc. - are being installed in an electric power distribution system in recent years. These distributed generators are not always generating steady power due to the weather conditions or hot-water demand conditions, etc. Therefore, DGs could make ldquobalanced three-phase loadrdquo unbalanced. Unexpected load unbalance creates many unpredicted problems in power distribution systems: voltage unbalances, frequency deviations, etc. It is also known that the loss minimum normal open sectionalizing switch positions for three phase unbalanced conditions are not the same as the ones calculated by assuming three-phase balanced. Therefore, a method to find the optimal normal open sectionalizing switch positions that minimize both distribution loss and three phase unbalance is required. The problem is the multi-objective planning problem, and the palate solution must be found. In this paper, a solution algorithm for loss minimum re-configuration is explained and several numerical examples are shown.