Due to strong coupling of grid-following converter

the relation between phase-locked loop(PLL)-based synchronization loop and DC-link voltage control(DVC)-based power balance is unclear. In this paper

the interaction analysis between these two controls is developed in the cases of bandwidth separation and bandwidth proximity. Firstly

based on control dynamic behaviors

the damping ratio and oscillation frequency are defined as PLL dynamic indexes

and the synchronous torque and damping torque are defined as DVC dynamic indicators. Then

by the singular perturbation analysis

the linear model established before is algebraically reduced in critical scene

and the interaction in the case of bandwidths separation is revealed by analyzing the changes in these dynamic indicators. Furthermore

based on the open-loop transfer function of DVC

the effects of PLL on the amplitude margin of DVC are analyzed to reveal the interaction in the case of bandwidths proximity. In particular

the impacts of terminal voltage control(TVC) are considered. It is found that the interaction between PLL and DVC is deteriorated with TVC bandwidth decreasing

leading to a reduction of the static stability limit and the instability disappearance in the case of bandwidths proximity.