Voltage and reactive-power control optimization in a distribution system

A new method is proposed for coordinating voltage/reactive-power control in a distribution system using a modified dynamic programming approach. The method is able to coordinate the action of substation on-load tap changer and the switching of substation and feeder capacitor banks that results in reduced distribution system losses, an improved voltage profile, and lesser tap changer and capacitor switching operations. Voltage limits of 0.95 and 1.05 per unit are imposed on feeder lines while reactive power flow through the main transformer is included in the cost by using the utility's power factor discount/penalty formula. Using a tap-estimator that searches for only the feasible tap settings reduces computational burden. The results of simulations show that the method is effective in bringing down costs in system operation.