A Closed-Loop Model for Stability Analysis of Grid-Connected Voltage-Source Converters

With an increasing number of grid-connected voltage-source converters in the power system, the stability analysis for the converter-grid interactions is of great interest. This paper proposes a linearized closed-loop model for predicting such stability problems, especially for those occurring under weak-grid conditions. Differing from the other known modeling approaches, a closed-loop model is constructed based on the transfer functions and it contains the control functions as well as the grid impedance. The stability and the individual controller impact can be assessed by the poles and zeros of the closed-loop transfer functions. Lastly, the linearized model is validated against the corresponding time-domain simulations and its excellent accuracy is proofed.