1 Index Terms—Control Techniques, Energy Storage, FACTS, Primary Frequency Control, SMES, STATCOM. I. INTRODUCTION N order to guarantee the operation security of the power system (PS) in case of an unexpected failure of some of its components, the generation units need to maintain short-term reserve not only in adequate quantity but also with a satisfac- tory dynamic response. In case this reserve is insufficient, as much in quantity as in speed, in order to compensate the power imbalance caused by the failure, under-frequency load shed- ding is employed as the last action taken for maintaining the system frequency within acceptable limits. This brings techni- cal and economic consequences that are related to costs of deficits. These costs depend on the amount of power discon- nected and the disconnection duration time. An alternative to effectively accomplish the operation security requirements is to use energy storage systems in combination with flexible al- ternating current transmission systems (FACTS) in such a way that active power can be injected, at a fast response, to the This work was supported in part by SECyT (Argentina) and CAPES (Bra- zil) under joint project Cod. BR/PA03-EX/022, No. 0.64/04 M. G. Molina and P. E. Mercado are with CONICET and the Instituto de Energía Eléctrica – UNSJ, Av. L. G. San Martín Oeste 1109, J5400ARL, San Juan – Argentina (e-mails: mgmolina@ieee.org, pmercado@ieee.org). E. H. Watanabe is with COPPE and the Laboratório de Eletrônica de Po- tência – UFRJ, P.O. Box 68504, Rio de Janeiro (RJ), 21945-970, Brazil (e-mail: watanabe@coe.ufrj.br ). electric network. In this way it is possible to take advantage of the better dynamic response of these integrated devices when compared to the response of generators. In recent years, it has been gradually seen that supercon- ducting magnetic energy storage (SMES) systems, have re- ceived considerable attention for power utility applications [1]. Due to the rapid advances in superconductive technology these units of reasonable size have been designed and commissioned successfully. In this way, SMES devices major characteristics, such as rapid response (ms), high power (hundred MW), high efficiency, and four-quadrant control can be used for enhanc- ing the dynamic operation security of power systems. By combining the technology of superconduction with the appropriate FACTS controllers, the PS can take advantage of the flexibility benefits provided by SMES coils and the high controllability provided by power electronics aiming at par- ticipating of the primary frequency control (PFC). Among the large variety of FACTS devices, converter-based (a.k.a. in- verters) controllers allow to incorporate a SMES device into the dc bus by using an appropriate interface. Within the last group, it has been suggested the use of Static Synchronous Compensators (STATCOM) as the most adequate for PFC [2]. This paper studies the dynamic performance of a STATCOM integrated with a SMES coil for improving the PFC of transmission systems. A model approach of both the STATCOM and the SMES device and a multi-level control scheme of the coordinated system are proposed. Finally, tech- nical analysis is performed, comparing the situation with and without STATCOM/SMES, to obtain conclusions about the benefits of using SMES devices in the PFC. All studies are performed through digital simulation carried out by using SimPowerSystems of SIMULINK/MATLAB™ on the Argen- tinean high voltage interconnected power system in conditions of sudden generation lost. II. MODELING OF THE STATCOM/SMES A STATCOM compensator is a self-commutated voltage source inverter-based device which acts as an ideal synchro- nous machine. It generates a balanced set of three sinusoidal voltages at the fundamental frequency, with controllable am- plitude and phase angle [3]. By maintaining the phase angle at zero (i.e. the output voltages of the STATCOM in phase with the line voltage) and varying the amplitude of the voltage pro- Analysis of Using FACTS Controllers with Superconducting Magnetic Energy Storage in the Primary Frequency Control of Power Systems M. G. Molina, Member, IEEE, P. E. Mercado, Senior Member, IEEE, and E. H. Watanabe, Senior Member, IEEE I 1-4244-0288-3/06/$20.00 ©2006 IEEE 2006 IEEE PES Transmission and Distribution Conference and Exposition Latin America, Venezuela