Simplified method of sequence impedance modeling of three-phase LCL inverter

Abstract

With a large number of distributed power sources connected to the grid, the distribution network is showing a trend of power electronics. As the inverter of the power conversion interface, the stability of its interaction with the grid cannot be ignored. Reasonable impedance modeling of the three-phase grid-connected inverter is the prerequisite for analyzing the stability and resonance characteristics of the grid-connected system. In this paper, firstly the harmonic linearization impedance modeling theory is briefly explained, including the establishment of the harmonic linearization model of the inverter main circuit and the phase-locked loop. Secondly, the traditional harmonic linearization impedance modeling process is analyzed, and it is pointed out that the modeling process requires many tedious phase sequence transformations and convolution operations. To solve this problem, a simplified modeling method is proposed on the basis of the traditional harmonic linearization method, which simplifies the modeling process. Using this method, the positive and negative sequence impedance model of the grid-connected inverter with capacitive current feedback control and grid voltage feedforward control strategy are established. Finally, the simulation verifies the accuracy of the impedance model.