Stability analysis of grid-connected converter based on interconnected system impedance modeling under unbalanced grid conditions

This paper investigates the interconnected system impedance modeling and stability analysis of grid-connected converter under unbalanced grid conditions. The proportional integral resonant (PIR) regulator is employed to control the negative sequence current. The comparison of negative sequence current suppression capability and system stability was analyzed between traditional proportional integral (PI) and the PIR regulator. The influence of the parameters in PIR regulator is also investigated. Finally, the simulation model is developed to validate the proposed impedance-based stability analysis criterion of grid connected converter.