Enhancing the Small-Signal Stability of Power Grids via Optimally Coordinating Inverter-Based Resources

Modern power systems with the high penetration of inverter-based resources (IBRs) commonly face phase-lock loops (PLLs)-dominated small-signal stability issues, especially in low short-circuit grids. These issues can be addressed by refining controllers' design of IBRs, which however fails to be effective when power grids are operating under some critical conditions. To this end, this paper presents a novel optimization model for coordinating active power outputs (i.e., operation adjustment) of IBRs while satisfying small-signal stability constraints (SSSCs). In particular, SSSCs are formulated based on a new metric that quantifies the small-signal stability from the viewpoint of grid strength, which is especially suitable for those "black-boxed" IBRs. To reduce the problem-solving complexity due to the inherent discontinuity and nonlinearity, a sequential solution approach is proposed to decompose the original optimization problem into a sequence of sub-optimization problems (SOPs). Also, a dynamical-region-adjustment method and a convex-relaxing method are integrated to ensure the existence of feasible solutions and further enhance the solution efficiency. Finally, the performance of the proposed method is verified based on two test power systems.