Study of STATCOM and UPFC Controllers for Voltage Stability Evaluated by Saddle-Node Bifurcation Analysis

One of the major causes of voltage instability is the reactive power limit of the system. Improving the system´s reactive power handling capacity via flexible AC transmission system (FACTS) devices is a remedy for prevention of voltage instability and hence voltage collapse. In this paper, the effects of two FACTS controllers, STATCOM and UPFC, on voltage stability will be studied. Continuation power flow (CPF), with accurate model of these controllers, is used for this study. Applying saddle node bifurcation theory with the use of power system analysis toolbox (PSAT), the optimal location of these controllers is determined. The study has been carried out on the 6-bus and IEEE 14-bus test systems and results are presented.