Simulation-based analysis of the interaction between grid-forming and grid-following inverters in an island grid

As part of the research project "Fuchstal leuchtet," building on previous findings from LINDA 2.0, the investigation focuses on how stable grid operation can be ensured in a purely inverter-based island grid. For this purpose, system operation is controlled using only the grid variables of voltage and frequency, reflecting interconnected grid behavior through the use of grid-forming and grid-following inverters. Within this paper, parameter settings and test scenarios based on manufacturer-specific RMS simulation models are developed to analyse the influence of outer-loop P(f)- and f(P)-control strategies of grid-forming and grid-following inverters on frequency behavior. By implementing various parameter scenarios and corresponding grid disturbances within the simulations, the study identifies which critical interactions can be revealed using RMS-simulation models. Based on these findings, it is evaluated whether stable island grid operation is possible using the applicable technical connection rules (TCR) for grid-following generation units and whether adjustments may be necessary. Therefore, parameter variations of grid-forming and grid-following inverters are analyzed regarding their impact on frequency dynamics and system stability in the island grid.