Stability Modeling, Analysis and Control of Grid-Following and Grid-Forming Inverters: A Koopman-Based Data Driven Approach

Microgrid (MG) system functionality is limited by low inertia, nonlinearity, dynamical operation regions and system and network dynamics. The proposed unique model-based method analyzes nonlinear dynamic behavior and parameter uncertainty propagation in inverter-based resource studies using Koopman mode-based eigen analysis and extending it to koopman-based predictive control (K-PC). The state-space (SS) model is then expanded by redefining uncertain components as pseudo-state variables. The modified system's dynamics can further be investigated across time using Koopman eigenfunctions, eigenvalues, and modes. Finally, frequency domain and a hardware-in-the-loop (HIL) based time domain analysis on a networked microgrid test system with grid-forming (GFM) and grid following (GFL) inverters confirms the proposed methodology.