A structure-preserving energy function for a static series synchronous compensator

It is currently not possible to effectively apply direct methods for transient stability assessment in general multimachine systems incorporating Static Series Synchronous Compensators (SSSCs) because present energy functions do not involve SSSC actions. This paper presents a way to incorporate the transient stability augmentation action of an SSSC into an energy function for multimachine systems. We first assessed damping control strategies for an SSSC using the control Lyapunov function theory. After making some assumptions a new term of a structure-preserving energy function (SPEF) that represents an SSSCs energy function was constructed. This term can simply be added to any existing SPEF. The extended SPEF was tested in longitudinal and IEEE nine-bus test systems. A comparison between critical clearing times (CCTs) acquired directly and those obtained by time simulation results show that the proposed SSSCs energy function is suitable and a proper CCT can be obtained.