Output impedance modeling of grid-connected inverters considering nonlinear effects

Accurate modeling of a single-phase grid-connected inverter with LCL filter considering the dead-time effects and nonlinear characteristics of switching devices is addressed in this paper. By comparing with the conventional averaged model and switching model, the equivalence of the derived model is verified. Further, an output impedance model of the grid-connected inverter is proposed and applied to the analysis of grid harmonic interactions. It is shown such a model can be used to identify the root cause of harmonic generation of grid-connected inverter systems. Theoretical analysis and simulation results are presented to demonstrate the effectiveness of the proposed output impedance modeling.