Impedance analysis is an effective method to analyze the oscillation issue associated with grid-connected photovoltaic systems. However

the existing impedance modeling of a grid-connected photovoltaic inverter usually only considers the effect of a single perturbation frequency

ignoring the coupling frequency response between the internal control loops of a grid-connected inverter

which severely affects the accuracy of the stability analysis. Hence

a method of impedance modeling and stability analysis for grid-connected photovoltaic inverters considering cross-coupling frequency is proposed in this paper. First

the generation mechanism of frequency coupling in grid-connected photovoltaic inverters

and the relationship between the coupling frequency and perturbation frequency are analyzed. Secondly

a sequence impedance model of grid-connected photovoltaic systems considering the coupling frequency is established by using the harmonic linearization method. The impact of DC bus voltage control strategy on frequency coupling characteristics of a grid-connected photovoltaic system is evaluated

and the impact of a coupling frequency term on system stability is quantitatively analyzed. Finally

the advantages of the proposed method are verified by several simulations. The results show that the proposed impedance model can accurately predict the potential resonance points of the system

and the coupling frequency characteristics will become much stronger with smaller DC bus capacitance or larger bandwidth of the DC bus controller.