Voltage stability improvement using Unified Power Flow Controller (UPFC): article

Voltage stability problem with voltage collapse as its final consequence is an emerging phenomenon in electrical power systems. In recent year, there are a lot of devices used to control the stability of voltage. One of the well known devices is the FACTS devices. There are many devices categorized under FACTS devices. One of the FACTS controllers is the Unified Power Flow Controller (UPFC). This paper presents the effectiveness of UPFC in controlling voltage stability of power system. UPFC is utilized in this study due to its versatile capabilities of line power flow regulation and oscillations damping; can provide simultaneous, real-time control of all basic power system parameters (transmission voltage, impedance and phase angle) and dynamic compensation of power system. A voltage stability index, namely Line Stability Index Lmn is used to indicate the stability of each line in the system. Several UPFCs are installed at selected lines in order to improve the voltage stability in the power system. The optimal sizings of UPFCs are identified using Evolutionary Programming (EP). The proposed optimization technique was validated on the IEEE Reliability Test System and indicating that the technique is feasible to be implemented in larger system.