Effects of SVC and TCSC Control Strategies on Static Voltage Collapse Phenomena Nemat Talebi M. Ehsan S.M.T. Bathaee Islamic Azad Univarsity Sharif University K.N.Toosi University Science and Reaserch Campus Electrical Enginerring Faculty Electrical Enginerring Faculty Nemat-Talebi@azad.ac.ir M.ehsan@sharif.ac.ir Bathaee@K.N.T.U.ac.ir Abstract: This paper focuses on detailed steady state models with emphsize on control loops of two Flexible AC Transmission System (FACTS) devices’ namely, Static Var Compensator (SVC) and Thyristor Controlled Series Capacitor (TCSC) , to study their effects on voltage collapse phenomena in power systems. Based on results at the point of collapse ‘ control loops strategies which could increase system loadability or increase loadability margin to collapse point are determined. The IEEE 14 bus test system is used to illustrate the effects of FACTS devices control strategies on voltage collapse phenomena. 1. Introduction Voltage collapse problems in power systems have been a permanent concern for the electric utilities, as several major black outs through out the world have been directly associated to this phenomena, e.g. WSCC July 1996 and etc. Many analysis methods have been proposed and currently used for the study of this problem [1,2,3]. Most of these thechniques are based on the identification of system equilibria where the corresponding jacobians become singular. These equilibrium points are typically refferd to as points of voltage collapse and can be mathematically associated to saddle-node bifurcation [4,5]. The voltage collapse points are also known as maximum loadability points. In fact, the voltage collapse problem can be restated as an optimization problem where the objective function is to maximize certain system parameters typically associated to load levels [6,7,8,9]. Hence, voltage collapse techniques may also be used to compute the maximum power that can be transmitted through the transmission system. In the new competitive energy market litretuers also known as total transfer capability or as available transfer capability [10]. It is well known that shunt and series compensation can be used to increase the maximum transfer capabilites of power networks [11]. With the improvments in current and voltage handling capabilities of power electronic devices that have allowed for development of flexible ac transmission system devices. The possibility has arisen to using different types of controllers for efficient shunt and series compensation. Thus, FACTS devices based on thyristor controlled reactors (TCR) such as static var compensators (SVC) and thyristor controlled series capacitors (TCSC) are being used by several electric utilities to compensate their systems [12]. Recently, various types of devices for shunt and series compensation based on voltage source convertors (VSC) 'namely, STATCOM , SSSC , UPFC , have been proposed and implemented [13]. This paper concentrate on studying the efffects of SVC and TSCS control loop strategies on voltage collapse phenomena using adequate steady state models of these devices [14]. Control loop strategies of FACTS devices are very different. Based on normal operation requirements of power system or an optimization objective function, the best control loop strategy for FACTS devices are adapted. Thus, during voltage collapse phenomena, each of these control loop strategies may have different interaction. So the interaction of FACTS devices on voltage collapse phenomena dependes on upon their control strategies. In the other word responses of FACTS devices on various operation condition of power system, are governed by control loop strategies. Therefore a control loop strategy may act on special phenomena, as an exciting or extingushing source. Section 2 briefly introduces the basic mathematical tools required for the analysis of voltage collapse phenomena. In section 3 detailed describtion of SVC and TCSC models and their various control loop strategies are given. Section 4 is depicted to simulation of voltage collapse phenomena on IEEE 14 bus test system with implementing SVC and TCSC. Finally, section 5 summrizes the main points of this paper and discusses future reaserch directions. 3 0-7803-8367-2/04/$20.00 ©2004 IEEE