Voltage/line stability indices assessment in a strategic dispatch of maximum reactive power with UPFC

Present power systems have become complex and heavily load ed, due to which voltage instability has become a serious problem, leading to Voltage Instability a cause of system collapse from which the system cannot recover. Real and Reactive power compensation in transmission systems improve the voltage stability of the AC system and can avoid voltage collapse. Maximum power transfer capability is achieved when the UPFC is operated at its rated capacity and conventional voltage and line-flow set point regulation is no longer possible. A dispatch strategy is proposed for a UPFC operating at rated capacity in which the power circulation between the shunt and series converters is used as the parameter to optimize the power transfer. In this paper voltage stability Lindex and three line stability indices have been discussed and are illustrated with the results obtained on a standard IFF 5 Test Bus system. Also by incorporating UPFC in the power flow control ,the impact of this device on voltage/line stability indices is investigated under simulated conditions on IEEE 5 Test Bus system.