Abstract: Small-signal modeling method is one of the main methods to analyze microgrid stability and design inverter controller.According to whether the dynamic characteristics of filters and lines to be considered or not,the small-signal models can be divided into the high-order model and the reduced-order model,thus the research takes the comparison of these two models into consideration.Considering the small-signal modeling of power loop,LC filter and line impedance,a high-order small-signal model for a single-inverter grid-connected system is built.Furthermore,the steady-state equation is used to describe the dynamic characteristics of the filter and the line,and the reduced-order model and error expressions of the system are obtained.After that,for the single-inverter grid-connected system,the correctness of the two small-signal models is verified by the simulation on the MATLAB/Simulink software.Then,the analysis of the eigenvalues,the main related status variables and error expressions demonstrates that the low frequency eigenvalues could be acquired accurately by the reduced-order model.In addition,by analyzing the parameter sensitivity values and root locus obtained by the two small-signal models,it is found that the effect of the reduced-order model in some occasions,such as low frequency oscillation analysis,damping analysis and controller design,is consistent with that of high-order model.But as the reduced-order model cannot obtain high and middle frequency eigenvalues,the stability analysis in low impedance ratio value network or inductive network may reach wrong conclusions.Finally,the correctness of these conclusions is verified by the root locus and power response waveforms.