Effects of strong resonance in multimachine power systems with SSSC supplementary modulation controller

SUMMARY The modal interaction between the electric power system modes due to the variation of parameters can cause strong resonance. The effect of strong resonance on these oscillatory modes can sometimes be a concern for the system stability. This article investigates the performance of these modes, the swing mode and the exciter mode, in the presence of a static synchronous series compensator damping controller. The relevant modes of interaction at strong resonance are identified—exciter mode is identified by the method of participation factors, whereas swing mode is identified by the concept of multimodal decomposition. Strong resonance is detected in full order system and reduced order system, which is based on the method of perturbations, suggested by Seyranian. A tuning method is also presented to design static synchronous series compensator damping controller and obtain optimal design parameters so that strong resonance can be mitigated. The systems of study include the three-machine 10-bus system, 4-machine 2-area system, a 4-machine 11-bus practical system—a part of the southern grid—an Indian power system, and a 10-machine 39-bus New England system. Copyright © 2011 John Wiley & Sons, Ltd.