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 thesis extends the functionality of D-FACTS concept by introducing variability in impedance injection of D-FACTS devices, thereby improving their controllability. Furthermore, this thesis presents a more detailed analytical treatment of such a topology termed enhanced Power Flow Controller (ePFC). It is shown that employing 1st order (assumes 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 provide more accurate steady state impedance over existing models are presented. Likewise, to analyze the stability of this system, Poincare mapping of entire bus-to-bus system is employed and the resultant dynamic model of an ePFC is systematically derived in this thesis. Also the effect of compensation L is determined. Finally, eigen values of this system are mapped as a function of conduction angle and regions of instability are identified for the enhanced Power Flow Controller.
