This paper deals with optimal power flow control in electric power systems by use of unified power flow controller (UPFC). Models suitable for incorporation in power flow programs are developed and analysed. The application of UPFC for optimal power flow control is demonstrated through numerical examples. It is shown that a UPFC has the capability of regulating the power flow and minimising the power losses simultaneously. An algoriithm is proposed for determining the optimum size of UPFC for power flow applications. The performance of UPFC is compared with that of a phase shifting transformer (PST).

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Abs tractThis paper deals with damping of power system electromechanical oscillations using controllable series compensators (series capacitors and phase shifters ) and controllable shunt capacitors. The study is based on investigation of the eigenvalues of a simple linearized power system model. The controllable series components are located on the transmission line connecting two areas and the controllable shunt capacitor is located close to a load. It is shown that the level of transmission line loading, load characteristics and inertia of the two areas influence the damping achieved by the controllable components to different degrees. The contributions of the controllable series components to the enhancement of power system damping for the same rating of the Controllable components are compared. Numerical examples are provided to verify the theoretical findings. The purpose of this paper is to provide an insight and understandings in the basic characteristic* of the d a m p ing effects of the studied devices. This insight is obtained by study of a simple power system that exhibits power oscillations. The understandings and findings can facilitate the analysis of realistic, and more complex power systems.