Thévenin Equivalent Representation of Meshed Grids for IBR Dynamic Phenomena Replication

Single inverter-based resource (IBR) infinite-bus representation has been adopted for real-world event analysis and replication by the senior authors. In particular, for the 2021 Texas Odessa event, adopting a Thévenin equivalent representation for the main grid and subjecting the grid voltage to a voltage dip enable successful demonstration of IBR bus phase jump. In this article, we provide the justification of the Thévenin equivalent representation by examining a meshed network with and without faults. Using the bus impedance matrix, we present the theoretic analysis that leads to the findings of Thévenin equivalent impedance and voltage before and during the fault. It can be seen that a fault causes dip in the Thévenin equivalent voltage and change in the equivalent impedance. Additionally, we have set up two test circuits, one meshed network with an IBR and another a single-IBR infinite-bus system. We conduct open-circuit and short-circuit tests for the meshed network at the IBR’s point of interconnection bus to demonstrate that the Thévenin equivalent representation based on the theoretic analysis matches with the one found from the experiments. Further, we show that for the same IBR, its dynamic performance in a meshed network for a fault is the same as that based on the single-IBR infinite-bus system subject to a voltage dip event.