Impedance modeling and stability analysis of LCL-type grid-connected inverters with different current sampling schemes

Two sequence impedance models of LCL-type grid-connected three-phase inverters with different current sampling schemes are presented using the harmonic linearization method, respectively. The proposed positive- and negative-sequence impedance models are then applied to analyze the stability and resonance between the converter and the grid. An impedance-based analysis approach is used to characterize such resonance caused by impedance interactions under grid-side current (GC) feedback and converter-side current (CC) feedback, respectively. Detailed circuit simulation is built to validate the accuracy of the impedance models as well as their effectiveness applied to the comparative analysis of stability margin of different current sampling schemes quantitatively.