Improvement of Voltage Stability and Reduce Power System Losses by Optimal GA-based Allocation of Multi-type FACTS Devices H.R. Baghaee, Student Member, IEEE, M. Jannati, B. Vahidi, Senior Member, IEEE, S.H. Hosseinian, H. Rastegar Electrical Engineering Department, Amirkabir University of Technology Hafez Ave, Tehran-Iran (phone: 0098-21-66466009; fax: 0098-21-66406469) E-mails: hrbaghaee@aut.ac.ir, mohsen.jannati@aut.ac.ir, vahidi@aut.ac.ir, hosseinian@aut.ac.ir, rastegar@aut.ac.ir Abstract— Modern power systems are prone to widespread failures. With the increase in power demand, operation and planning of large interconnected power system are becoming more and more complex, so power system will become less secure. Operating environment, conventional planning and operating methods can leave power system exposed to instabilities. Voltage instability is one of the phenomena which have result in a major blackout. Moreover, with the fast development of restructuring, the problem of voltage stability has become a major concern in deregulated power systems. To maintain security of such systems, it is desirable to plan suitable measures to improve power system security and increase voltage stability margins. FACTS devices can regulate the active and reactive power control as well as adaptive to voltage- magnitude control simultaneously because of their flexibility and fast control characteristics. Placement of these devices in suitable location can lead to control in line flow and maintain bus voltages in desired level and so improve voltage stability margins. This paper presents a Genetic Algorithm (GA) based allocation algorithm for FACTS devices considering Cost function of FACTS devices and power system losses. Proposed algorithm is tested on IEEE 30 bus power system for optimal allocation of multi-type FACTS devices and results are presented. Keywords— Voltage Stability, FACTS Devices, Optimal Allocation, Genetic Algorithm. I. INTRODUCTION MODERN, power systems are prone to widespread failures. With increased loading of existing power- transmission systems, operation of power system becomes more complex and power system will become less secure. Operating environment, conventional planning and operating methods can leave systems exposed to instabilities. Voltage instability is one of the phenomena which have result in a major blackout. Besides, with the electricity market deregulation, number of unplanned power exchanges increases due to the competition among utilities and direct contracts concluded between generation companies and costumers. If these exchanges are not controlled, some lines may become overloaded. Because many of the existing transmission lines could not cope with increasing power demand, the problem of voltage stability and voltage collapse has also become a major concern in planning and operation of deregulated power systems. So control of power flow in order to have more efficient, reliable, and secure system is in the interest of the transmission system operator (TSO). To overcome this problem, FACTS devices are introduced. FACTS devices can regulate the active and reactive- power control as well as adaptive to voltage magnitude control simultaneously by their fast control characteristics and their continuous compensating capability and so reduce flow of heavily loaded lines and maintain voltages in desired level. Besides, FACTS devices can improve both transient and small signal stability margins. Controlling the power flows in the network, under normal and abnormal conditions of the network, can help to reduce flows in heavily loaded lines, reduce system power loss, and so improve the stability and performance of the system without generation rescheduling or topological changes in the network [1]. Because of the considerable costs of the FACTS devices, it is so mementos to find out the optimal location for placement of these devices to improve voltage stability margins and enhance network security [2-7]. Effect of FACTS devices on power system security, reliability and loadability has been studied according to proper control objectives [5-15]. Some of papers have been tried to find suitable location for FACTS devices to improve power system security and loadability [14-17]. Optimal allocation of these devices in deregulated power systems has been presented in [18-19]. Some of papers use heuristic approaches and intelligent algorithms to find suitable location of FACTS devices [16-19]. In [20], voltage stability index has been used to find the suitable location of UPFC to improve power system security/stability after evaluating the degree of severity of considered contingencies. This paper presents a novel heuristic method based on GA to find optimal location of multi-type FACTS devices to enhance voltage stability level considering investment cost these devices and power system losses. Genetic Algorithm is previously used for many optimization problems like optimal power flow, economic dispatch and controller optimization, congestion management and etc in power systems [21- 23]. Proposed method is tested on IEEE 30 bus system and results are presented. Authorized licensed use limited to: B.P. Poddar Institute of Management & Technology. Downloaded on October 14, 2008 at 14:14 from IEEE Xplore. Restrictions apply.