Mechanisms and suppression methods of interaction oscillations in complex inverter networks under weak grid conditions

Under weak-grid conditions, coupling between grid-connected inverters and grid impedance can excite high-frequency oscillations. This paper develops a modular small-signal model that maps local VSC state-space models to a global dq-domain nodal-admittance matrix. Modal sensitivity and participation factors are used to identify the dominant resonant mode and its contributing components. Based on this diagnosis, a participation-factor-guided HPF active-damping strategy is designed, with an analytical nominal gain and a full-order robust correction accounting for digital delay and grid-impedance uncertainty. Simulations of a three-VSC ring network, including comparisons with CCF-AD and GCF-AD over SCR=1.2–2.5, demonstrate improved high-frequency damping with limited fundamental-frequency error and control effort.