The oscillation problem of the grid-connected system with the inverter as the energy interface occurs frequently

to improve the immunity of the inverter usually introduces the voltage feed-forward sector in the control structure

however

the feed-forward control will significantly change the operating characteristics of the inverter

which in turn affects the stability of the system. Therefore

this paper investigates the effect of feedforward control on different oscillation dominant sectors and proposes an additional feedforward oscillation suppression method. Firstly

the frequency-coupled impedance model of the inverter is established

and the effects of feedforward control on the impedance characteristics of different frequency bands are analyzed. Secondly

the dominant sector of oscillations in different frequency bands are clarified. Then

the mechanism of system instability triggered by the interaction between the dominant sector of oscillations and the grid

taking into account the feed-forward control

is analyzed. Then

based on the uncertainty and disturbance estimator

an oscillation suppression method is proposed for the phase-locked loop band. Compensating the perturbation of the phase-locked loop as an additional feed-forward sector to the q-axis current loop can effectively improve the impedance characteristics of this band and thus suppress the oscillation. The results show that the voltage feedforward control with a scaling factor of 1 and the additional feedforward control based on UDE can effectively improve the stability of the system current loop and phase-locked loop frequency bands

and the effectiveness of the proposed method is verified by time-domain simulation.