Homogeneity Realization for Cluster of Heterogeneous Grid-forming Inverters

This paper presents a control scheme for enforcing coherency in a cluster of grid-forming inverters with heterogenous characteristics. Increasing penetration of distributive generation (DG) drives the conventional grid towards more complex structure and a new concept with heterogenous characteristics known as power electronics dominated grid (PEDG). Thus, it becomes more challenging to optimize and perform various analysis without an accurate model that mimics the large-scale networks dynamics. The aggregated and reduced-order models that accurately represent the full-scale network enables optimal coordination and computationally efficient stability assessment in real-time. However, the heterogenous characteristics of the inverter based DGs due to the different filter model parameters, inverter ratings and control algorithms poses a challenge to derive an accurate aggregated model. This paper proposes to acquire homogenous dynamic characteristics via coherency enforcement control to aggregate the cluster of grid-forming inverters into single equivalent model that can accurately predicts the dynamic of a PEDG cluster. The coherency in the dynamic response of the grid-forming inverters is realized by autonomously identifying and emulating an equivalent inertia. Various case studies are presented in this paper that validates the proposed enforcing coherency control scheme.