Aggregated and Reduced-Order Admittance-Based Modeling of Converter-Interfaced Resources for Power Systems Transient Analysis

The proliferation of converter-interfaced resources (CIRs) in power grids has highlighted the need for their accurate and efficient modeling. This paper proposes an aggregated and reduced-order admittance-based modeling (ARO-ABM) method for multi-converter systems, aimed at achieving efficient time-domain simulations. First, the nonlinear subsystems of the grid-following CIR with slow dynamics, i.e., the phase-locked loop (PLL) and power controller, are linearized. Then, both the fast (linear) and slow (linearized) subsystems of the CIR system are integrated into a unified admittance-based transfer matrix model. Subsequently, the obtained admittance models of the CIRs, combined with the impedance of the collector lines, facilitate the proposed aggregated modeling of multi-converter systems. This aggregation, followed by model-order reduction, reduces the computations and simplifies the evaluation of the overall dynamic behavior of the multi-converter system, as seen from the external power network. The accuracy and computational improvement of the proposed ARO-ABM are verified through simulations using MATLAB/Simulink.