Under high permeability, the interaction between a grid-connected inverter (GCI) and high grid impedance may lead to system instability. The current control of a GCI can be divided into proportional resonance (PR) control in the phase domain and proportional integral (PI) control in the dq domain according to different control domains. First, considering the frequency coupling effect, the sequence admittance models of the LCL GCIs with PR control in the phase domain and PI control in the dq domain are respectively established based on an harmonic linearization method. Then, the sequence admittance characteristics of the two GCIs are compared and analyzed considering the impact of the grid voltage feedforward. Based on the established sequence admittance models and generalized Nyquist criterion (GNC), the influence of the grid voltage feedforward and grid stiffness on the stability of the two GCI systems controlled in different domains is analyzed. The stability analysis results show that the stability of a PR-controlled GCI system in the phase domain is stronger than that of a PI-controlled GCI system in thedomain without considering the grid voltage feedforward, while the stability of the two GCI systems is basically the same after introducing the grid voltage feedforward. Finally, simulations verify the correctness of the theoretical analysis.