With the rapid development of new power system

renewable energy is gradually dominating the stability characteristics of power system. In this paper

the synchronization stability mechanism and stability improvement technology of grid-following inverter in weak grids is researched. Firstly

the impact of synchronization methods on stability is analyzed. The instability mechanisms of two synchronization methods

namely phase locked loop (PLL) based and PLL-less method

are analyzed. It could be summarized as that due to the coupling effect between the synchronization part and current loop

the current reference deviate from the expected control target. Secondly

from the perspective of weakening the coupling effect

a synchronization decoupling control strategy based on the instantaneous reactive power theory is proposed. Then

the initial parameter values are designed using time-domain indicators. A sequence impedance model considering frequency coupling effect is established

and the stability of the proposed strategy is analyzed using impedance stability criteria. Finally

experimental validation work is carried out. The synchronization decoupling control strategy demonstrated good stability and robustness under different grid strength conditions. The proposed strategy could not only improve the small disturbance synchronization stability

but also significantly enhance the transient synchronization stability.