Evaluation of Synchronous Condensers in Modern Power Grids for Enhancing Grid Stability

Abstract

Abstract As renewable energy sources increasingly replace conventional synchronous generation, the resulting decline in system inertia and reactive power capability presents growing challenges for maintaining power system stability. Synchronous condensers (SCs) offer a potential solution by enhancing voltage stability through high fault current injection, providing dynamic reactive power support, and contributing to frequency stability via rotational inertia. This thesis investigates the ability of SCs to improve power system stability, with a focus on voltage regulation and frequency support. Simulations were conducted in DIgSILENT PowerFactory on two grid models of varying strength and complexity, referred to as the robust grid and the islanded grid. Three SC ratings, 8 MVA, 67 MVA, and 200 MVA, were evaluated to determine their effectiveness under different fault scenarios and deployment strategies. In the robust grid model, SCs had a limited impact on mitigating voltage dips due to the high short-circuit capacity (SCC) of the system and in the case of a short distance between the SC and the fault. However, notable voltage recovery improvements were observed under weakened grid conditions and at more vulnerable locations. Performance between the 67 MVA and 200 MVA units was similar, though deploying multiple smaller SCs may provide redundancy benefits. Regarding frequency support, the high system inertia in the robust grid limited improvements in the rate of change of frequency (RoCoF) and frequency nadir, which were more evident in the islanded model. In the weaker islanded system, the deployment of an 8 MVA SC significantly improved both voltage and frequency stability. The SC effectively mitigated voltage dips, enhanced voltage recovery, and improved the Ro- CoF and frequency nadir during disturbances. Its positive impact was consistent across all placement locations, making the deployment strategy less critical. These results highlight the value of SCs in supporting voltage and frequency stability, particularly in low-inertia systems, more vulnerable grids, and weak points within robust networks.