Small-signal stability bounds with cross coupling

Determine bounds on the dynamic droop coefficients of grid-forming inverter-based resources that ensure small-signal stability while fully accounting for the impact of active-power–voltage-magnitude and reactive-power–frequency cross coupling.

Background

The paper introduces dynamic droop coefficients as frequency-dependent transfer functions that characterize the small-signal relationship between an inverter-based resource’s active and reactive power deviations and its AC frequency and voltage-magnitude deviations. For simplicity, the main analysis neglects the off-diagonal cross-coupling terms, although the full model includes them.

The authors note that existing decentralized stability conditions are limited primarily to single-input single-output bus dynamics. Establishing coefficient bounds that guarantee small-signal stability for the full multi-input multi-output bus dynamics, including cross coupling, would extend the proposed specifications and improve their ability to assess interconnected grid-forming inverter-based resources.