International Electrical Engineering Journal (IEEJ) Vol. 5 (2014) No.12, pp. 1639-1648 ISSN 2078-2365 http://www.ieejournal.com/ 1639 Venkateswara and Kumar Firefly Algorithm based Optimal Power Flow with Static VAR Compensator for Improvement of Power System Security under Network Contingency Abstract— At present owing to the increase in power demand power system have become more complex and heavily loaded, and are subjected to unstable or insecure operations. In order to provide a secure operation of the power system, it is needed to enhance the level of a security margin to the power system. In this paper Firefly algorithm based Optimal Power Flow used to select the optimal sizing of SVC which minimizes the total real power generation cost is proposed. New indices like Line security index and voltage security index are defined for measuring Power system security. This paper was also deals with the impact of SVC under network contingency with Firefly Algorithm based Optimal Power Flow. The results were presented for 5 bus system and modified IEEE 30 bus system without and with SVC in normal operating condition as well as network contingency by using Firefly Algorithm based Optimal Power Flow. The results obtained with Firefly optimization technique was compared with Genetic Algorithm (GA). Index Terms— Flexible AC Transmission System, Firefly Algorithm, Optimal Power Flow, Static VAR Compensator.. I. INTRODUCTION Power systems are becoming increasingly more complex due to the interconnection of regional system and deregulation of the overall electricity market. It has been required to better utilize the existing power networks to increase capacities by installing FACTS controllers. The variables and parameters of the transmission line, which include line reactance, node complex voltages are able to be controlled using FACTS controllers in a fast and effective way. The benefits derived from FACTS include improvement of the stability of power system networks, such as voltage stability, line stability, small signal stability, transient stability, and thus enhance system reliability [1, 2]. However, controlling power flows is the main function of FACTS. Transmission lines in congested areas are often driven close to or even beyond their limits in order to satisfy the increased electric power consumption. So secure operation and reliable supply is imperiling by the higher risks for faulted lines [3]. But the construction of additional power lines is often difficult for environmental problems, economical problems and political problems. In these conditions the technology of FACTS provides a significant opportunity [4]. Power system is a complex network consisting of more number of generators, transformers and transmission lines. Failures of one or more transmission lines lead to outages. Outage of transmission line is called network contingency [5, 6]. Out of the several preventive and corrective measures suggested in literature to protect power system networks against voltage collapse because of line outage, the placement of FACTS controllers has been established as an effective means. Out of all FACTS devices static VAR compensator (SVC) has been widely used in power systems. This is a shunt connected FACTS device. They can provide rapid control of the susceptance and in turn the reactive power supply to transmission lines, which maintain the node voltages at or near a constant level and enhancing the power transfer capability [7, 8]. The rapid response feature of SVC also provides many other opportunities for improving power system performance. This paper presents a new Meta heuristic optimization technique called Firefly Algorithm has been introduced to find the optimal location of SVC device to improve power system security. Its performance is compared with Genetic Algorithm (GA) [9, 10] technique. The real and reactive power generation values and voltage limits for buses are taken as constraints, along with susceptance limits of the SVC, during the optimization. Computer simulations using MATLAB were done for the 5 bus system and modified IEEE 30 bus system and active power losses, voltage profile have been consider to compare the Genetic Algorithm based Optimal Power Flow with Firefly Algorithm based Optimal Power Flow. This paper also deals with SVC incorporated in GA based Optimal Power Flow and Firefly Algorithm based Optimal Power Flow in contingency analysis to reduce the losses and minimize the total real power generation and to enhance loading margin under severe contingencies. Firefly Algorithm based Optimal Power Flow with Static VAR Compensator for Improvement of Power System Security under Network Contingency B.Venkateswara Rao * , G.V.Nagesh Kumar * * GITAM University , Visakhapatnam, Andhra Pradesh, INDIA Corresponding Author: gundavarapu_kumar@yahoo.com