Ehsan Heidari - Department of Computer Engineering, Islamic Azad University, Doroud Branch, Doroud, Iran
Reza Saki
Faranak Nikabadi

With increased power transfer, transient stability is increasingly important for secure operation. Transient stability evaluation of large scale power systems is an extremely intricateand highly non-linear problem. An important function of transient evaluation is to appraise the capability of the power system to withstandserious contingency in time, so that some emergencies or preventive control can be carried out to prevent system breakdown. Inpractical operations correct assessment of transient stability for given operating states is necessary and valuable for power system operation. UPFC(Unified Power flow controller) controller is FACTS device which can be used to control active and reactive power flows in a transmission line. The damping ofpower system oscillations after a three phase fault is also analyzed with the analyzation of the effects UPFC on transient stability performanceof a power system. This paper presents the HGAHGAPSO optimization of the parameters of a fuzzy controller for UPF Causing a HGAPSO algorithm to enhance the transient stability performance of power systems. Computer simulation by MATLAB results on a 2-area 4-machine 12-bus power system with an UPFC installed between buses s and r confirm the efficacy of the new approach in damping the local-mode and inter-area mode of oscillations.

transient stability, UPFC, HGAHGAPSO, Fuzzy controller