Dynamic Behavior of Grid-forming Inverters in Large-scale Low-strength Power Grids

The massive integration of variable renewable energy (VRE) generation based on grid-following inverters (GFL), along with the decommissioning of synchronous generators (SG), are weakening the power grids and reducing their stability margins to unprecedented levels. Conventional solutions such as synchronous condenser (SC) have been implemented to cope with the challenge of maintaining system strength and stability in grids with high levels of VRE. Grid-forming inverter (GFM) is an emerging technology that aims at emulating the grid attributes provided by SG; however, GFM capabilities have only been demonstrated in small-scale simulation environments and microgrids. This paper is a first attempt to model and assess the dynamic behavior, interaction, and system-wide impact of GFM in a large grid modeled in EMT software. Different types of GFM control methods are modeled and simulated to identify the minimum capacity required to maintain strength and stability in the grid. The results showed that a good dynamic performance can be achieved using GFM technology in low-strength grids.