In power systems with high penetration of renewable energy, dynamic issues associated with multi-device interaction involving DC voltage control (DVC) and AC current control (ACC) of power electronic (PE)-interfaced devices are constantly emerging. The device participates in the interaction dynamics based on the way that DVC adjusts the current reference of ACC to regulate the internal voltage amplitude/frequency under the active/reactive power imbalance. Thus, to analyze the effect mechanism of the device on system dynamics, the device should be characterized as internal voltage in response to power imbalance stimulation. However, the existing modeling works fail to recognize the process of the device participating in system dynamics, so the regulation mechanism of the internal voltage by the device under power imbalance for the system dynamics analysis remains unclear. Therefore, this paper proposes a modeling method of the PE-interfaced device based on the recognition of the regulation process of the internal voltage amplitude/frequency by the device under the active/reactive power imbalance. The model based on power-imbalance stimulation and internal-voltage response relationships is first established to characterize the regulation by detailed controls. Since the stimulation-response relationships are dominated by DVC, to directly describe the regulation by DVC, the model with ideal ACC is further proposed through the infinity gain equivalence of ACC. Based on the model, the characteristics of the device in DVC timescale and the impact mechanism of the device on system dynamics by regulating the internal voltage amplitude/frequency are revealed. Simulation results for verification are also included.