Probabilistic evaluation of transient stability of a power system incorporating a UPFC

This paper presents a probabilistic based approach to evaluate transient stability of power systems incorporating a unified power flow controller (UPFC). In this application, the UPFC is employed to boost the transmission system capacity and the system voltage after fault clearing and, therefore, enhances the system stability. In this context, investigations have been conducted on a sample multi-machine power system taking into consideration the uncertainty of several factors associated with the practical operation of the power system. A risk index that reflects the likelihood that the system encounters an instability problem is presented. The effect of load forecast uncertainty on such an index is also investigated.