Impact of secondary voltage control on voltage stability

In this paper, different operation modes of secondary voltage control in voltage instability conditions are investigated. The voltage instability considered here is caused by a critically high system load level. This level is determined and studied in the presence of the primary voltage control and in the presence of both the primary and the secondary voltage controls. The system behavior is analyzed next, using the method of dynamic bifurcation. Finally, an emergency assist mode of secondary voltage control in voltage instability conditions is proposed and examined.