Modeling and analysis of an ePFC (enhanced power flow controller) with conduction angle control

Series Flexible AC Transmission Systems (FACTS) devices have been employed to increase power transfer capability of transmission networks and to provide direct control of power flow over designated transmission routes. However, high costs and reliability concerns associated with implementing one large FACTS device capable of altering the power flow in a wide transmission network have limited widespread deployment of FACTS solutions. Recently, concept of Distributed FACTS (D-FACTS) was proposed as an alternative approach to realize cost-effective power flow control through multiple, small, fixed series impedance injections. This paper extends the functionality of D-FACTS concept by introducing variability in impedance injection of D-FACTS devices, thereby improving their controllability. Furthermore, this paper also presents a more detailed analytical treatment of such a topology termed enhanced Power Flow Controller (ePFC). It is shown that employing 1st order (assume s sinusoidal voltage across compensation capacitor) and 2nd order (assumes sinusoidal current in the transmission line) fundamental impedance model are inaccurate methods to analyze effective impedance inserted by ePFC. Instead, a new mathematical model that is based on sinusoidal voltage difference between two end buses is proposed. The efficacy of this approach and its advantages as compared to existing models are presented.