Integrating Grid-Forming Inverter-Based Resources Into Ac Power Flow Cascading Outage Simulations

Cascading outage simulation has been studied primarily in the context of synchronous generator-dominated power systems. However, with the increasing penetration of inverterbased resources (IBRs), particularly of grid-forming (GFM) type, renewed attention is required. This paper proposes an enhanced AC power flow (AC PF)-based cascading outage simulation method that incorporates the impact of GFM IBRs, specifically addressing their fault ride-through (FRT) capability and IBRs trip in case of non-compliance. To achieve this, an extended AC power flow model is developed, which includes a steady-state representation of GFMs and refined frequency- and voltage-dependent models for synchronous machines, replacing the conventional simplified PV bus model. Case studies conducted on the IEEE 39-bus system validate the applicability of the proposed method under various initial events, showing that non-FRT-compliant IBRs can trip during or immediately after fault, altering dramatically the path and outcome of the cascade. While conventional AC PF methods fail to converge in these scenarios, the proposed approach successfully evaluates the system state at each tier of the cascade, accurately simulating system behavior throughout the cascading outage. The proposed approach provides a deeper understanding of cascading outage behavior in power systems with high penetration of GFM IBRs.