All Nodes Voltage Regulation and Line Loss Minimization in Loop Distribution Systems Using UPFC

Voltage regulation and line loss minimization in distribution networks are challenging problems, particularly when it is not economic to upgrade the entire feeder system. This paper presents a new method for achieving line loss minimization and all nodes voltage regulation in the loop distribution systems, simultaneously, by using unified power flow controller (UPFC), one of the most important FACTS devices. First, the line loss minimum conditions in the loop system are presented. Then, load voltage regulation is applied under line loss minimum conditions. Reference voltage of the controlled node is determined based on the assumption that this voltage can subsequently improve all node voltages to be within the permissible range. Also, the proposed control scheme of the UPFC series converter, to regulate all node voltages under line loss minimization, is presented. The effectiveness of the proposed control scheme has been experimentally verified.