Controlling the flow of real and reactive power

The unified power flow controller (UPFC) is the cornerstone of EPRI's flexible AC transmission system (FACTS) program. FACTS is an evolving technology-based solution envisioned by EPRI to help the electric utility industry deal with the changes in the power delivery business. UPFC was proposed for real-time control and dynamic compensation of AC transmission systems and offers multiple compensation functions. Using it makes control of all three parameters of AC transmission systems possible: voltage; line impedance; and phase angle. Control of these parameters can be carried out simultaneously or sequentially with transfer from one type of control to another in real-time. This functional flexibility offers a great potential in solving many of the problems facing the electric utility industry.