A Review: Voltage Stability and Power Flow Improvement by Using UPFC Controller

Load demand nowadays is increasing sharply and to meet that demand, boost in generation capacity is needed. Voltage instability occurs because of external and internal unbalance due to which bus voltage change. Unified Power Flow Controller (UPFC) is a FACTS device to achieve the constant voltage and increase power flow in transmission line. This paper presents the analysis of UPFC to control both active and reactive power and also discusses the comparison of other FACTS devices. As compared to other FACTS devices like STATCOM control only voltage, TCSC and SVC controls only impedance, but UPFC is one of the most promising FACTS device to control phase angle, voltage magnitude, impedance and various line parameters selectively or simultaneously. It also discusses in detail UPFC topology in transmission line.