Modeling and Stability Analysis of Multi Grid-Forming Converters With Connected to Low-Impedance Grid

Stable operation of multi grid-forming converters will suffer from integration into low-impedance grid, because of strong coupling between voltage sources which include the multi grid-forming converters and AC grid. This paper contributes to giving physical insights into stability of multi grid-forming converters with connected to low-impedance grid. To start with, dynamical model of multi grid-forming converters is presented to depict damping and synchronizing components for quantitative analysis of system stability. On the basis, self-stability and en-stability components are proposed to characterize the interactions among grid-forming converters. Stability mechanism of multi grid-forming converters is revealed by studying the evolution law of self-stabilizing and en-stabilizing damping components with variation of grid impedance or converter control parameters. It is indicated that interactions among grid-forming converters will become more serious with decrease of interconnection line impedance or transmission line impedance, worsening stability of system. Finally, theoretical analysis is verified with time-domain simulation and experimental results.