International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056 Volume: 06 Issue: 09 | Sep 2019 www.irjet.net p-ISSN: 2395-0072 © 2019, IRJET | Impact Factor value: 7.34 | ISO 9001:2008 Certified Journal | Page 2106 Improvement of Voltage Stability by Placing UPFC using fuzzy Logic G. Sudeep 1 , V. Suryanarayanareddy 2 1 Academic Consultant, Dept. of. Electrical and Electronics Engineering, SVU College of Engineering, S V University, Tirupati, A.P, India 2 Assistant Professor Dept. of. Electrical and Electronics Engineering -------------------------------------------------------------------------***------------------------------------------------------------------------ ABSTRACT - Increase in electrical demand due to increase in population and modernization necessitated increase in the power generation with adequate increase in electrical infrastructure. Owing to lack of generation, existing infrastructure, operating power system with large interconnected system becomes more complex causing voltage instability, power loss and unreliable operation of power systems. In this paper, voltage instability is addressed using optimal placement of UPFC using fuzzy logic. The simulation has been conducted on IEEE 14 bus system using Mi Power software package. The results obtained through simulations have ensured the effectiveness of fuzzy logic for UPFC placement to accelerate the significant improvement of voltage stability. Keywords: Unified Power Flow Controller (UPFC), Contingency ranking, fuzzy logic, voltage sensitivity index, optimal power flow, voltage stability and Flexible AC transmission Systems (FACTS), optimal placement. I. INTRODUCTION Modern electrical power systems are highly complex in nature and aim to meet the increasing power demand with acceptable power quality and affordable electricity price to the consumers. The financial and environmental issues enforce the placement of power generating units at places away from load centers. The restructuring of power system networks has augmented the uncertainties in system operation [1, 4]. The regulatory constraints on the extension of the transmission network has resulted in declining of the stability limits and increased the risks of cascading failures and blackouts. This problem can be sorted out by the introduction of high-power electronic controllers for the regulation of voltages and power flows in AC transmission systems [1-6]. The FACTS is a model depends on the power electronic controllers, which boosts the value of transmission systems by enhancing power transfer capability. These controllers operate at very high speed, leads to safe operating limits of a transmission system with acceptable stability. The evolution in the FACTS was triggered by the development of new solid- state electrical switching devices. The FACTS devices are mainly classified to three types, Series Devices, Shunt devices and Shunt series devices the effectiveness of FACTS devices in improving the performance of a system depend on 1. The placement of the device in the power system network. 2. The size of the devices. 3. The type of the device, i.e. shunt or series type. 4. The type of control strategy employed. The main advantages of FACTS devices are,  Increases 20-30% transfer capacity. Power flow control  Enhance the stability of power system.  Efficient use of existing infrastructure. In this paper, the optimal location of UPFC has been carried out on IEEE 14 bus to boost the voltage stability margin. The load index, voltage and percentage active power loading of the transmission lines are taken into account for deciding the optimal location of the UPFC. To verify the accuracy of the explored optimal location, the enhancement of voltage profile has been tested by connecting UPFC at that transmission line.