Design and performance evaluation of subsynchronous current suppressor with SSSC

A long transmission line needs controllable series as well as shunt compensation for power flow control and voltage regulation. This can be achieved by suitable combination of passive elements and active FACTS controllers. In this paper, series passive compensation and series active compensation provided by a static synchronous series compensator (SSSC) are considered. This paper presents investigation of subsynchronous resonance (SSR) characteristics of the hybrid series compensated power system and proposes a novel method for the extraction of subsynchronous component of line current using filter. The extracted subsynchronous frequency component of line current is used to modulate the SSSC injected voltage which suppresses subsynchronous current in the transmission network. This novel technique is termed as Subsynchronous Current Suppressor (SSCS). The design of SSCS is based on damping torque analysis. The results show the effectiveness of SSCS in damping in SSR. The 3-phase model of the SSSC is based on the switching functions. By neglecting harmonics in the switching function, D-Q model is derived which is combined with similar models of the other system components for linear analysis. The results of the linear analysis are validated by carrying out transient simulation based on the detailed nonlinear models.