Category: Physics

Summary: Finding when bridge-concentrated inertia deficits and stressed tie lines shift the dominant reactive mode of an islanded microgrid onto inter-island bridge buses.

Bridge nodes in an islanded microgrid can carry disproportionate responsibility for keeping separate regions dynamically coordinated. This experiment asks when concentrating inertia weakness at those bridges, together with stressed tie-line loading, causes the dominant reactive mode to stop reflecting whole-island motion and instead localize on the bridge structure itself.

The model constructs dense symmetric reactivity operators for modular microgrid ensembles and uses GPU eigensolves to track the leading mode across increasing system sizes. An iterative-deepening threshold search narrows the coupling value where the dominant pattern changes character and concentrates on bridge buses.

That is a targeted structural question rather than a generic stability check. The result is intended to map when a weakly supported connector becomes the preferred site of system-wide vulnerability in modular low-inertia grids.

Method: GPU dense symmetric eigensolves with iterative deepening and bisection on tie-line stress and bridge-focused inertia concentration in microgrid reactivity operators.

What is measured: Critical coupling threshold, localization of the leading reactive mode, bridge-bus concentration, system size reached, and bracket width.