Abstract
Both tap-changer transformers and static VAR compensators can contribute to power systems voltage stabilities. Combining these two methods is the subject of this paper. Effect of the presence of tap-changing transformers on static VAR compensator controller parameters and ratings required to stabilize load voltages at certain values are highlighted. The interrelation between transformer off nominal tap ratios and the SVC controller gains and droop slopes and the SVC rating are found. For any large power system represented by its equivalent two nodes system, the power/voltage nose curves are found and their influence on the maximum power/critical voltage are studied.