Detection of Sub-Synchronous Control Interaction (SSCI) Using Modal Identification Analysis and FFT

All power electronic control systems in the vicinity of series compensated lines are susceptible to Sub-Synchronous Control Interaction (SSCI). Any contingency which results in a radial condition between power electronic systems and series compensated lines can trigger an undamped SSCI oscillation. This is a purely electrical phenomenon and grows very fast in the scale of a few hundreds of milliseconds. This paper proposes an effective and reliable algorithm to detect and trip SSCI within 150ms. The proposed solution utilizes mode identification approaches in parallel with moving FFT in d-q reference frame to capture the frequency and magnitude of oscillations and process them to issue reliable trip command in the case of SSCI. A detailed model of 90MW wind farm connected to a series-compensated line was developed and the protection algorithm was tested under SSCI condition. The proposed method successfully tripped within the acceptable time frame.