Geometric Decentralized Stability Condition for Power Systems Based on Projecting DW Shells

The development of decentralized stability conditions has gained considerable attention due to the need to analyze heterogeneous multi-converter power systems. A recent advance is the application of the small-phase theorem, which extends the passivity theory. However, it requires the transfer function matrix to be sectorial, which may not hold in some frequency range and will result in conservatism. This letter tackles this problem by leveraging the Davis-Wielandt (DW) shells for decentralized stability analysis. We develop a geometric decentralized stability condition that visually displays how heterogeneous converters interact with the power grid and enable modular system analysis.