Aggregated and Reduced-Order Admittance-Based Modeling for Efficient Small-Signal Analysis of Power-Electronic-Based Power Systems

Aggregation and model-order reduction techniques may be applied to parts of large-scale power grids where the detailed dynamics of individual components are not necessary, thus enhancing the efficiency of the overall simulation. This article proposes an aggregated and reduced-order admittance-based modeling (ARO-ABM) that enables efficient and accurate time-domain simulations of power grids with converter-interfaced distributed energy resources (DERs). The ABMs of converter-interfaced resources (CIRs) with diverse structures and parameters are formulated as transfer functions. Then, the transfer-function-based ABMs of CIRs are aggregated along with their collector lines and impedance/ admittance-based model (I/ABM) of any other connected components, such as loads. The use of I/ABMs enables scalable aggregation of all CIRs, including those with fully known dynamic models, as well as those whose models may not be disclosed by manufacturers. This step is followed by the model-order reduction in the frequency domain. These steps result in the reduction of the computational complexity of the individual subsystems. The proposed method is demonstrated to enable the use of larger simulation time steps while maintaining good accuracy in offline (MATLAB/Simulink) and real-time (OPAL-RT) simulations of power-electronic-based power systems.