Dynamic similarity analysis for active distribution grid equivalents

The increasing share of inverter-based resources (IBRs) has reshaped distribution–transmission dynamics. Capturing their fast control interactions via electromagnetic transient (EMT) simulations are computationally demanding, necessitating effective aggregation and reduction methods for grid equivalents. This work proposes novel network reduction techniques and a sophisticated methodology to assess the dynamic similarity of grid equivalents. The aggregation techniques involve an iterative process employing Kron reduction and an optimisation-based approach. The validation of the dynamic similarity of the aggregated models is based on time and frequency domain. The resulting reduced networks enable the incorporation of the network system dynamics into large-scale system studies in a computationally efficient way. The proposed methodologies were tested in a case study and their appropriateness was verified. This has the potential to improve study results for appropriate power system planning and operation.