Increasing penetration of power electronic (PE) grid-tied devices has caused more and more dynamic problems with unknown mechanisms. Since grid operation asks for a certain voltage amplitude and frequency level when there is a power imbalance

roles of the PE grid-tied devices during dynamics must be characterized as internal voltage response under power excitation

in which the voltage vector evolves through its time-varying amplitude and frequency. Existing modeling works

unfortunately

fail to recognize amplitude and frequency modulation essence of grid voltage during dynamics

so corresponding linear models are inapplicable to small-perturbation grid dynamic analysis. Thus

taking current control timescale of grid-tied voltage source converter (VSC) for example

this paper establishes a model with active and reactive current excitation and internal voltage amplitude and frequency response. Especially

the role of the terminal voltage detection-based phase-locked loop (PLL) in the excitation-response relationship is revealed. Linearization is conducted by clarifying amplitude and frequency operating points and corresponding increments of AC signals. This model intuitively reflects the evolution of internal voltage amplitude and frequency excited by active and reactive currents

which represents characteristics of the device during dynamics. Then

simulations for verification of the linear model and time-varying nature of amplitude and frequency are presented. Features of the characteristics of VSC are preliminarily discussed.