As it is

the grid-connected inverter usually works under the condition of unbalanced grid voltage

unbalanced grid impedance and unbalanced filter inductance. This paper studies impedance modeling and stability analysis of grid-connected inverters under the unbalanced operation conditions. Firstly

under the conditions of unbalanced voltage at the point of common coupling and unbalanced inverter filter inductance

the relationships between the voltage imbalance component

the filter inductance and the harmonic component are derived. Then the output admittance model of the grid-connected inverter in the positive sequence and negative sequence coordinates are developed. Thus the analytical expression of the admittance matrix is obtained

and the characteristics of the positive-sequence

the negative-sequence and the coupling admittances are analyzed. Based on the generalized Nyquist stability criterion and the unbalanced admittance expression of the inverter

the stability analysing criterion of the inverter in the unbalanced situation is given. Finally

experimental results are given to verify the stability criterion.