Regarding a grid-following PMSG system

there exists internal coupling related to multiple loop controls and external coupling representing the interaction between the generator and the grid. Such internal and external couplings can introduce additional paths for PLL

and may affect the synchronization performance of the system. Therefore

this study establishes the synchronization mechanism of the PMSG system by taking into account the internal and external couplings and reveals the mechanism of generator instability. Firstly

focusing on the interaction between the PMSG and the grid

this study explores PLL as a coupling bridge between them

and investigates the impact of various grid conditions on the system stability. The study also considers the dynamic behavior of the DC bus voltage and examines the intrinsic mechanism of the interaction between the machine side converter and grid side converter of PMSG. By employing a complex torque analysis method

the study analyzes the influences of internal multiple-loop control parameters and external grid conditions on the equivalent damping of the system. In accordance with the effects of internal and external couplings

a coordinated control strategy for improving the equivalent damping torque of the PMSG is proposed. The research results demonstrate that the additional paths introduced by internal and external couplings can alter the structure of the PLL and weaken its equivalent damping. However

compensating for the negative damping introduced by this coupling can reshape the equivalent damping of and enhance the synchronization stability of the PMSG. Finally

the theoretical analysis is validated and the effectiveness of the improved control strategy is demonstrated through experimental prototypes.