The impedance-based stability analysis is an effective method used in the analysis of subsynchronous oscillation (SSO) of wind farm. Based on the harmonic linearization theory, the impedance model of grid-connected D-PMSG is proposed, the main contribution is considering the frequency coupling of output currents. Firstly, the frequency coupling characteristic of phase locked loop (PLL) is analyzed. Then, the harmonic components in control loop are calculated. Finally, the impedance of PMSG look inside from PCC is established, and the mechanism of sub/sup-synchronous currents coupling is analyzed quantitatively. Simulation are carried out to verify the correctness of the theoretical analysis.

impedance modeling,D-PMSG,frequency coupling,harmonic linearization,sub/sup-synchronous oscillation