Frequency Domain Fitting of Grid-connected Inverter's Impedance

In order to solve the stability problem caused by the interaction between the inverter side and the grid side when a large number of distributed grid-connected inverters are connected to the public grid, the frequency domain fitting method is introduced into the analysis of new power system in this paper. In this paper, the frequency domain fitting method of transfer function is introduced firstly, and then the process of generating system equations required by the method when the system contains control and nonlinear parts is demonstrated by taking a single grid-connected inverter closed-loop system as an example. In this method, the transfer function of the grid-connected inverter under any given input and output can be obtained only by the topology structure information and control strategy information of the grid-connected inverter. The frequency domain fitting method effectively avoids the tedious problem of deriving the equivalent output impedance manually for the stability analysis of power electronic converters under different topologies and control strategies. This method can fit the topology and control strategy of the new grid-connected inverter effectively in frequency domain.