A unified flow control concept for flexible AC transmission systems

The control of an AC power system in real time is involved because power flow is a function of the transmission line impedance, the magnitude of the sending and receiving end voltages, and the phase angle between these voltages. It has been long realized that an all solid-state or advanced, static VAR compensator, which is the true equivalent of an ideal synchronous condenser, is technically feasible and, with the use of gate turn-off (GTO) thyristors, is economically viable. This uniform approach of power transmission control promises simplified system design, reduction in equipment size and installation labor, improvements in performance, and significant reduction in capital cost that is fueled by advances in power semiconductor technology. The objective of this paper is to outline the technical and economical factors which characterize the uniform, all solid-state power-flow controller approach for real time controlled, flexible AC transmission systems. (CACT).