A Study on the Possibility and Countermeasures of Sub Synchronous Oscillation in Korea Power Grid

On April 28, 2025, Spain experienced Sub-Synchronous Oscillation (SSO) caused by high penetration of inverter-based renewable energy in a weak grid environment with low Short Circuit Ratio (SCR), along with a blackout. This study simulates a comparable event in the Korean power grid using PSS/E. A three-phase fault in the Anjwa region resulted in voltage oscillations. After the voltage exceeded 1.1 pu, which led to the tripping of 6 GW of renewable generation, the frequency dropped below 59.3 ㎐, causing a further 4.5 GW of renewable generation to disconnect. STATCOM and GFM-ESS were implemented to mitigate voltage oscillations through dynamic reactive power support. Further analysis using PSCAD on a simplified grid revealed that the Power Plant Controller (PPC), combining VQ and PF control, effectively resolved the oscillation problem.