[Objective] To address the transient stability challenges in grid-following and grid-forming (GFL-GFM) converters parallel system

this paper proposes a transient stability control method based on dynamic adjustment of inertia-damping. [Methods] Firstly

a two-stage transient control framework was established for the GFL-GFM converters parallel system. During the fault period

fault current limiters were rapidly activated to mitigate overcurrent

while in the post-fault recovery stage

the phase-locked loop (PLL) of GFL converter and the inertia-damping parameters of GFM converter were dynamically adjusted. Secondly

the Sigmoid function was adopted to achieve inertia-damping coordination tuning

and the controller parameters were adaptively adjusted by the trend of the power angle of the parallel system. Finally

a time-domain simulation model of the parallel system of GFL-GFM converters was established based on the Matlab/Simulink platform. Through comparisons with traditional control methods and tests under voltage sag conditions of varying degrees

the effectiveness of the proposed transient control method was verified from multiple aspects. [Results] The results showed that compared with the traditional PLL freezing of GFL converter and the additional power control strategy of GFM converter

the proposed control method significantly reduced the amplitude of the power angle oscillation of GFL-GFM converters

greatly shortened the oscillation period

and adapted well to both mild and severe voltage sag conditions. The proposed control method effectively ensured the transient stability of the GFL-GFM converters parallel system during the whole fault process

and it also reduced the power angle oscillation deviation by more than 5%. [Conclusion] The proposed method enhances the adaptability and robustness of GFL-GFM converters parallel system under voltage sag of varying degrees

providing a new idea for the stable operation of grid-connected system with high proportion of power electronic equipment

which has good application value.