Slow-Interaction Converter-Driven Stability in the Distribution Grid: Small-Signal Stability Analysis With Grid-Following and Grid-Forming Inverters

Inverter-based resources (IBRs) are changing the dynamics of medium-voltage distribution grids (MVDGs), leading to concerns over slow-interaction converter-driven stability (SICDS). Although researchers have proposed numerous device-level solutions for IBR stability, culminating in the promotion of grid-forming (GFM) as opposed to grid-following (GFL) inverters, a system-level analysis from the point-of-view of the distribution system operator (DSO) is still lacking. As a first step toward standardization, this article provides some guiding principles for DSOs to prevent SICDS issues in MVDGs, by performing small-signal stability analysis and selecting a set of key parameters from state-of-the-art GFL and GFM models. By imposing bounds for these key parameters, DSOs could manage small-signal interactions between IBRs, as exemplified in the last section of this article over a 2-IBRs study case, later scaled to a multi-inverter configuration with five inverters in a CIGRE medium voltage distribution benchmark network.