Power Flow Control by Unified Power Flow Controller

The demand of energy usage is increasing rapidly and to meet the energy requirements, best possible transmission systems should be adopted to avoid energy losses in our transmission systems. In Pakistan's WAPDA (Water & Power Development Authority) system, the rapid increase in load and less generation capacity has increased load shedding thought the country. The government has planned to increase the generation capacity but the supply companies are facing line load-ability, environmental constraints, power limitations problems etc. Most of the supply companies prefer to extend the existing electrical networks instead of building new network to reduce financial burdens. In this paper the implementation of the FACTS (Flexible AC Transmission Systems) Devices in an electrical network is described. The FACTS devices enhance power transfer capacity of the line without adding new transmission line. These devices also protect the system from overloading in case of any contingency in the electrical network. The control of power flow, reactive power compensation and voltage control are the main capabilities of FACTS devices. This paper describes the impacts of FACTS devices on improving the voltage stability and power handling capability of a transmission line. The proposed methods for the controllable flow of active and reactive power in a transmission line are also elaborated. A simple electrical system is examined to explain the improvement in the constraints of power system using FACTS devices.