Due to the dynamic interaction between the permanent magnetic synchronous generator (PMSG) and the voltage source converter-based high voltage direct current (VSC-HVDC)

the PMSG-based wind farm via the VSC-HVDC system may experience oscillatory instability. Additionally

the dynamic characteristics of PMSGs in PMSG-based wind farm may differ due to differences in output active power or control parameters. However

existing studies on small-signal stability often ignore these differences in PMSG dynamic characteristics

leading to errors in small-signal stability analysis results. To address this issue

we analyzed the system's small-signal stability in the timescale of DC voltage dynamics considering the PMSG dynamic characteristics differences. Firstly

a reduced-order model of the system in the timescale of DC voltage dynamics was derived. Then

the relationship between the sum of the real parts of the oscillation modes and the PMSG's output active power or control parameters was analyzed based on this reduced-order model. The research shows that the sum of the real parts of the oscillation modes in the reduced-order model exhibits a linear relationship with the PMSG output active power

the proportional coefficient of the DC voltage control outer loop

and the proportional coefficient of the PLL. Based on this analysis

an average power or control parameter model is proposed to quickly and accurately assess the system's small-signal stability. Finally

the effectiveness of the proposed method and conclusions are verified through simulation examples.