Modeling and stability analysis of grid-tied VSC considering the impact of voltage feed-forward

Abstract

The single-input and single-output (SISO) transfer functions are proposed in this paper to analyze the impact of voltage feed-forward (VFF) loop on the stability of grid-tied voltage-source converter (VSC). Based on the SISO transfer functions, the VFF’s impacts are analyzed by considering the influence of current control integral time constant (ITC) and the grid impedance ratio X/R. To be specific, the VFF can improve the stability when the VSC has a large ITC, while it can decrease the stability when the VSC has a small ITC. The impedance ratio X/R is another affecting factor to the VFF when the phase-locked loop (PLL) dynamics are included in the transfer function model. The closed-loop poles of the VSC without the VFF loop are sensitive to the decrease of X/R, while it is not very susceptible to the variation of X/R when the VFF loop is applied in VSC. The proposed SISO transfer functions and stability analysis are both verified through simulations.