Comparing the voltage control capabilities of present and future VAr compensating techniques in transmission systems

The phenomenon of transient voltage stability in power transmission systems is explained. A generic method is used to examine the dynamics of stabilization as influenced by mechanically switched shunt capacitors and by static compensators. A comparison is made for the voltage stabilizing performance of different configurations of static VAr compensators. Technical merits of newly developed devices, such as voltage-source GTO converter based VAr compensators and thyristor-controlled series capacitors, in terms of counteracting voltage instability are also examined. A newly developed special controller for SVC schemes with TCR in transmission systems is presented. The controller ensures a stable opemion of the load intercmwting network at the usually unstable region where conventional SVC controls are void.