Discrete-time modeling and stability analysis of grid-connected inverter based on equivalent circuit

This paper presents a simplified discrete-time modeling and stability analysis method for digital controlled grid-connected inverters. Based on state-space average approximation, the dynamic of the original grid-connected inverter system is analyzed using the discrete-time model of the corresponding state-space average equivalent circuit. Compared to the conventional discrete-time modeling, this new approach has almost the same reliability and accuracy in stability prediction. In addition, the new model is more convenient for digital control design than the conventional discrete-time model due to its obvious simplicity. The simplified discrete-time modeling approach is validated by simulation and experiment.