Identification Modeling of Frequency-Coupling Admittance for Grid-Connected Inverter Under All Operating Conditions

The control structure and parameters of the grid-connected inverter in actual projects are usually unknown, which results in the “black-box” phenomenon. The traditional impedance modeling method is not suitable for the black-box. In this paper, a black-box identification method for the admittance of grid-connected inverters under all operating conditions considering frequency-coupling is proposed. Firstly, accurate discrete admittance data are acquired by the frequency-coupling admittance measurement. Then, the vector fitting (VF) is applied to identify the frequency-coupling admittance under a single operating condition. The black-box models identified by VF are combined with the weighting function to obtain the black-box admittance model of the grid-connected inverter under all operating conditions. Finally, the effectiveness and accuracy of the method are verified via MATLAB/Simulink. The results show that the method introduced in this paper not only can obtain the black-box admittance model under all operating conditions simply through several groups of admittance data, but also has the advantages of efficiency and high accuracy.