An Improved UPFC Control to Enhance Power System Stability

This paper presents an application of Single- Input Fuzzy Logic Controller (SFLC) to determine the control signal of Unified Power Flow Controller (UPFC) for improvement of power system stability. This compensation scheme relevant to Flexible AC Transmission systems (FACTS) technology is used worldwide to improve system dynamic performance. The UPFC is one of the most versatile flexible AC transmission system devices, which can be used to control the active and reactive power flows in a transmission line by injecting a variable voltage in series and reactive current in shunt. The SFLC uses only one input variable which is called as signed distance. The SFLC has many advantages: The total number of rules is greatly reduced compared to existing fuzzy logic controllers (FLC’s), and hence, generation and tuning of control rules are much easier. The proposed control method is applied to Single Machine Infinite Bus (SMIB) System to improve the transient stability.