Main transformer ULTC and capacitors scheduling by simulated annealing approach

In this paper, a simulated annealing approach is used to find the optimum schedule of the main transformer under load tap changers (ULTC) and shunt capacitors in a distribution system. The main purpose of this paper is to determine a proper schedule of the main transformer. ULTC position substation capacitor and feeder capacitors based on forecast hourly loads of each feeder and primary bus voltages such that the voltage deviation on the secondary bus can be decreased, the reactive power flow through the main transformer can be restrained, and the total feeder loss can be reduced. The constraints that must be considered include the voltage deviation limit on the main transformer secondary bus and along each feeder and the maximum allowable number of switching operations in a day for ULTC and each capacitor. In order to reach the objectives with these constraints on, a simulated annealing approach is employed to achieve a proper schedule. The presented approach can solve the complex and nonlinear optimal problem and reach a nearly optimal solution. To demonstrate the usefulness of the proposed approach, main transformer ULTC and capacitors scheduling in a distribution system within a service area of Yunlin District Office of Taiwan Power Company is performed. It is concluded from the results that the proposed approach is very effective in reaching proper dispatching schedule.