Decentralized Small Gain and Phase Stability Conditions for Grid-Forming Converters: Limitations and Extensions
For power system engineers, this work provides less conservative and more scalable decentralized stability certificates for converter-dominated grids, extending prior methods that were limited by sectoriality assumptions.
The paper addresses the limited applicability of decentralized small-gain and small-phase stability criteria for grid-forming converters due to the non-sectoriality at low frequencies. By introducing loop-shaping transformations, the proposed method resolves this issue and reduces conservativeness, enabling practical decentralized stability certification on the IEEE 14-bus network.
The increasing share of converter based resources in power systems calls for scalable methods to analyse stability without relying on exhaustive system wide simulations. Decentralized small gain and small-phase criteria have recently been proposed for this purpose, but their applicability to grid forming converters is severely limited by the sectoriality assumption, which is not typically satisfied at low frequencies. This work revisits and extends mixed gain phase conditions by introducing loop shaping transformations that reformulate converter and network models in alternative coordinate frames. The proposed approach resolves intrinsic non sectoriality at low frequencies and reduces conservativeness, thereby improving the applicability of decentralized stability certification. Analytical results are illustrated using an infinite bus system first and then extended to the IEEE 14 bus network, demonstrating the practicality and scalability of the method. These findings provide a pathway toward less conservative and more widely applicable decentralized stability certificates in power grids.