Admittance-Based Aggregated Modeling of Converter-Interfaced Resources With Heterogeneous Parameters for Transient Analysis of Multiconverter Systems

Aggregated modeling of converter-interfaced resources (CIRs) can decrease the computational complexity in time-domain simulations of electric grids with high penetration of renewable sources. This article presents admittance-based aggregated modeling (ABAM) for grid-following CIRs. The aggregation is carried out by representing the CIRs’ current controllers and output filters using transfer functions and aggregating them as admittances and sources. For improved aggregation accuracy, the CIRs are grouped in terms of their ratings, synchronization system parameters, and collector system parameters. The numerical advancements of the proposed ABAM are shown in an example renewable energy system consisting of multiple grid-following CIRs. It is verified that the ABAM has low sensitivity to the parameters and excellent accuracy in capturing the dynamics of heterogeneous CIRs compared to the conventional preserved-structure aggregated model with weighted-mean parameters. The proposed ABAM also permits the use of large time-step sizes with acceptable numerical accuracy in (offline) MATLAB/Simulink and (real-time) OPAL-RT simulators.