The delivery of wind or photovoltaic power via high voltage direct current(HVDC)system is an important approach to transmit power for large-scale renewable power bases. The sub/super-synchronous oscillation(SSO/SupSO)issues associated with wind farm is worthy of further study

especially the SSO/SupSO caused by the interaction between the direct-drive permanent magnet synchronous generator(D-PMSG)based wind turbines and the voltage source converter based HVDC(VSC-HVDC)system. Firstly

the dynamic models of D-PMSG and VSC-HVDC are established

and the interface matrix and interface dynamic equation between D-PMSG and VSC-HVDC are deeply analyzed and deduced. Then the complete dynamic model of D-PMSG interfaced with VSC-HVDC system is obtained. On this basis

the eigenvalue analysis method is applied to calculate the participation factors of the oscillation modes. At the same time

according to the participation factor of each mode

it can be concluded that there is damping coupling between the SSO mode and the SupSO mode. The time domain simulation by PSCAD/EMTDC verifies the correctness of the model and eigenvalue analysis results. Furthermore

this paper studies the influence of D-PMSG grid-connected distance/impedance

machine-side controller(MSC)/grid-side controller(GSC)of D-PMSG

sending-side controller(SEC)/receiving-side controller(REC)of VSC-HVDC system on the damping characteristics of SSO/SupSO. The results show that the same controller parameter will affect several SSO/SupSO modes

and the same SSO/SupSO mode will be affected by several controller parameters at the same time. The effect of damping coupling may exhibit convergence(the damping ratios of two coupling modes change in the same direction when adjusts controller parameters)

or anti-convergence(the damping ratios of two coupling modes change in the opposite direction when adjusts the controller parameters)

or both of convergence and anti-convergence.