Model Reduction of Electromagnetic Transient Dynamics For Inverter-Based Grids: An Interconnected Systems Framework

We propose a systematic framework for constructing reduced-order models of electromagnetic transient dynamics in inverter-based grids while preserving network structure. Specifically, the framework partitions an electrical grid into user-defined subsystems. Each subsystems’ state-space representation is systematically derived using the Component Connection Method and subsequently reduced in a method agnostic manner. Finally, we derive a lower-order approximation of system-level dynamics by interconnecting all subsystem-level models. We demonstrate the accuracy and scalability of the proposed framework using a modified version of the WSCC 9-bus system and the IEEE 24-bus system. In addition to studying singular perturbation, balanced truncation, and Krylov interpolation based reductions, we highlight the importance of methods that can also account for inter-subsystem dynamics. Finally, we implement the proposed framework in an open-source package to allow researchers and practitioners to readily create and reduce user-defined grids.