Distributed Droop-Free Control of Grid-Forming Inverters with Dynamic Line and Load Modeling

RESUMO

Droop-free distributed control has emerged as a promising alternative to conventional linear droop control for coordinating inverter-based resources in AC microgrids. However, existing droop-free methods typically rely on quasi-steady state network models that neglect fast electromagnetic transients and assume a decoupled dependence of active and reactive power on frequency and voltage, respectively. In this paper, we propose a transient-aware droop-free distributed primary/secondary control framework for grid-forming (GFM) inverters. The control objective is to achieve proportional active and reactive power sharing, frequency regulation, and voltage regulation within prescribed bounds. The proposed approach incorporates dynamic models of network lines and loads into the control design, enabling accurate representation of transient behavior while capturing the coupled nature of power flow interactions. A gradient-based distributed control update is derived from an optimization formulation, in which voltage magnitude constraints are enforced through a projection operator. To validate the performance of the proposed control, real-time simulation studies are conducted on a four-inverter microgrid under load changes in both strong and weak grid conditions. The results demonstrate that the proposed method improves transient performance, particularly in weak grids, while preserving the same steady state operating conditions as existing QSS-based droop-free approaches.