This paper conducts research based on the frequency coupling mechanism of grid-connected systems. Through theoretical analysis, the mathematical relationship between coupling frequency and system oscillation frequency has been derived. The sequence impedance model for droop control is established using harmonic linearization method. Based on the model, a quantitative formula for the frequency coupling degree of the system is proposed, and a coupling strength evaluation system is constructed. Finally, a SOGI control strategy based on virtual inductance is proposed to suppress frequency coupling characteristics, and the correctness of the theoretical analysis is verified through simulation results.