Proceedings of the PowerUp Conference

Small-signal instabilities, such as unforced sub- synchronous oscillations (SSOs), are increasingly observed in inverter-based resource (IBR) dominated grids. While decentral- ized stability certificates offer a scalable means to avoid instability onset, they are typically derived under restrictive network-state assumptions–such as small angle differences or negligible voltage drops–that cannot capture how departures from these conditions affect system stability. In this paper, we develop a network model and a decentralized analysis framework that explicitly characterizes how reactive power mismatches, line loading, and inverter control parameters jointly determine small-signal stability. We show that increased steady-state reactive power mismatches and line loading lead to more stringent conditions on admissible inverter droop gains. These results make decentralized stability certificates explicitly network-state dependent, showing how network stress shrinks the set of stabilizing local controller parameters.