Slow-interaction Converter-driven Stability in the Distribution Grid: Small Signal Stability Analysis using RMS Models

Massive integration of converter-interfaced generators has led Enedis - major French DSO - to inquire about the impact of multiple inverters equipped with closed-loop voltage control in the distribution grid, particularly in terms of slow-interaction converter-driven instabilities. In this paper, we employ RMS models in a small signal stability analysis to study the behavior of an inverter connected to a single-line equivalent representation of the upstream network, taking into account some particularities of the distribution grid. Assessing the behavior of system eigenvalues with respect to inverter measurement delay, we conclude that weak grid configurations may lead distribution networks to instabilities similar to those observed in transmission. A simplified reconfiguration example is used to reproduce low-frequency oscillations in time-domain simulation for a long distribution line.