Impedance Modelling and Stability Analysis of Grid-Connected Inverters with Power Loop and Feedforward Control

With the large-scale grid connection of new energy equipment, impedance modelling has become a key method for system stability analysis. Existing research has failed to fully meet the demands of practical engineering applications, with limited analysis of multi-link joint modelling incorporating power loops and feedforward control, as well as investigations into their impedance characteristics and inter-stage coupling effects. Taking the LCL inverter as the subject of study, this paper proposes an impedance modelling method incorporating the power loop, active damping, and voltage feedforward. Models are established in both the dq-domain and sequence-domain, analysing the influence of each control module on impedance characteristics and inter-sequence coupling. Frequency mapping-based disturbance injection is employed for full-band frequency sweeping, with theoretical and simulation results demonstrating high consistency, thereby validating the model's accuracy. Stability analysis demonstrates that time-domain simulations align with model predictions, confirming the model's reliability for stability assessment.