Aggregated modelling of multi-GFMC systems under current saturation

With the high penetration of renewable energy in modern power systems, the deployment of grid-forming converters (GFMCs) has increased significantly, owing to their inherent capabilities of voltage and frequency support. However, the high-order nonlinearity and mode-switching dynamics of GFMCs with current limiters pose enormous challenges to the modelling of multi-GFMC systems under faults. To address this problem, this paper investigates the aggregated modelling of multi-GFMC systems under current saturation caused by grid faults. By analyzing the key factors that affect the similarities of power angle curves among individuals, a coherency criterion is proposed to divide the converter group into distinct coherent groups. Under the premise of ensuring similar power dynamics among converters, the equivalent parameters of the coherent groups are calculated, and an equivalent aggregated model for the Multi-GFMC system under current saturation is established. Finally, a simulation model of 12 GFMCs integrated into the IEEE 39-bus power grid is developed in the MATLAB/Simulink platform to validate the accuracy of the proposed equivalent aggregated model.