The Unified Power Flow Controller (UPFC) is a typical FACTS (Flexible AC Transmission Systems) device that is the most sophisticated and complex power electronic equipment and has emerged for the control and optimization of power flow and also to regulate the voltage in electrical power transmission system. This paper propose the real, reactive power and voltage control through a transmission line by placing UPFC at the sending end using computer simulation. The L index is the parameter which is used to check the stability. Voltage stability is concerned with the ability of a power system to maintain acceptable voltages at all buses under normal conditions and after being subjected to a disturbance. The assessment of voltage stability has also become more complicated due to strengthening of power systems. The research work mainly dealt with performance analysis of IEEE-14 bus system for voltage stability, computation of voltage collapse point and enhancement of power system stability by using UPFC.