Inertia provision in distribution networks: assessing low-frequency oscillation risks among grid-forming converters

The increasing penetration of renewable energy sources at all levels of the power system, particularly within the distribution network, presents significant challenges aggravated by the decommissioning of synchronous generators. This shift reduces the overall system inertia, impacting the system dynamics and stability and requiring new solutions. One promising approach is the deployment of grid-forming converters, which can provide virtual inertia not only at the transmission level but also within the distribution network. This paper explores the risks associated with converter interactions in the distribution grid, specifically focusing on the dynamics between virtual synchronous machine-based converters. It analyses how the provision of virtual inertia influences oscillation damping, revealing that higher inertia can lead to reduced damping and increased risks of adverse effects on the distribution network. Finally, the paper emphasises that inertia provision by inverters must be accompanied by a damping contribution to reduce the risk of poorly-damped converter interactions.