Designing of a fuzzy-sliding mod Controller for UPFC to Improve the Transient Stability

An UPFC may be applied for steady-state power-flow and voltage control as well as for mastering dynamic phenomena like transient-stability margin enhancement, oscillation damping, etc. For these tasks the Lyapunov energy-function approach is frequently used as a convenient way to control or analyze the electric-power system (EPS). The basis for the implementation of such an approach is to know the energy function of the EPS. Currently, this is not possible for the EPSs that include UPFCs, because the already known energy functions that proved to be suitable for an EPS do not include such a device. In the present paper, the convenient operation and control of UPFC for transient stability improvement are considered. Considering that the system’s Lyapunov energy function is a relevant tool to study the stability affair. UPFC energy function optimization has been used in order to access the maximum of transient stability margin. In order to control UPFC, a fuzzy-sliding mod (FSM) and PI controller have been used. The designing results have been studied by the simulation of a single-machine system with infinite bus (SMIB) and another standard 9-buses system (Anderson and Fouad, 1977).