Location of shunt compensation devices is important for the enhancement of the voltage stability for practical power systems. This paper presents a comparison of several voltage stability indices in electric power system to identify the weakest bus/ area of the system. Shunt FACTS controller is introduced at the weakest bus in IEEE 14-bus test system and its effectiveness is assessed by comparing voltage profile and loading margin enhancement. Various line stability indices are also compared with and without shunt FACTS controller. It is shown that the best location for reactive power compensation for improving static voltage stability margin is the "weakest bus" of the system.

In this paper the application of an Static Var System (SVS) auxiliary controller for damping torsional oscillations in a series compensated power system is presented. A new auxiliary controller, known as the combined derivative of reactive power and derivative of computed internal voltage (CDRPDCIVA) auxiliary controller has been developed and incorporated in the SVS control system located at the middle of a series compensated long transmission line. Studies are conducted on a system having a similar spread of the torsional modes as the first IEEE benchmark model. The proposed SVS auxiliary controller stabilizes all the torsional modes for wide range of series compensation at a high power transfer level.