Implementation of unified power flow controller and verification for transmission capability improvement

This paper describes a unified power flow controller (UPFC) miniature model developed for performing system feasibility studies. The system and control configuration of the model are first described, then protection and control for transmission capability improvement are verified using a real time analog simulator. The series portion of the UPFC has three control modes (perpendicular voltage control, impedance control and voltage angle control) which are used for power flow control and/or power system stabilizing control. Various tests were performed to compare control modes. The perpendicular voltage control is proposed as the simplest and most practical mode because the capacity of the shunt compensator is minimized, and power flow control sensitivity is maintained over a wide range of angle