Stability assessments are crucial in transitioning towards a reliable renewable power system. An early identification of potential challenges allows transmission system planners to implement sustainable and cost-effective measures, ensuring stable grid operations. In this context, modeling the interaction of converter-based generation in active distribution networks with the transmission network is vital. Complexity-reduced equivalents of distribution network models facilitate comprehensive stability studies by reducing the computational load to a feasible level. This work introduces a novel method for creating equivalent distribution network models that is based on aggregating generators and loads of the detailed network model. Impedances connect the resulting aggregated components, forming the equivalent network model. This method is validated across various scenarios of grid-forming converter penetration and grid strength, and is compared with three established methods. The findings reveal that models aggregated with the industry standard method exhibit significant deviations from the detailed models and often fail to identify instabilities. Furthermore, the drawbacks of each established method are identified. In contrast, the proposed method successfully creates equivalent models that do not exceed any validation threshold values. Therefore, this work highlights the importance of employing appropriate methods for creating equivalent distribution networks to avoid erroneous assessments of system stability. • We conduct a sensitivity analysis for grid aggregation methods for future active distribution networks. • We demonstrate that industry standard REI method is not suitable for stability assessments. • We introduce the novel General Clustering Approach, as state of the art methods do not meet quality standards.
Ungerland et al. (Wed,) studied this question.