Large-Signal Modeling of Grid-Following Inverter: from Sixth-Order Model to Second-Order Model

As penetration of wind power plants increases, the grid condition becomes increasingly weaker, which may make grid-following (GFL) inverters lose synchronization under large grid disturbances. In prior research, most researchers study transient stability of GFL inverters based on a simplified second-order model. Namely, the focus is solely on dynamics of phase-locked loop. However, this simplified second-order model may lose partial accuracy. Moreover, the reasonability of the simplification has not been clearly clarified. To fill this research gap, this paper provides a deduction process from an accurate high-order model to several reduced-order models. It is found that when the dynamics of filter capacitors are ignored, the accuracy of the model is still high. However, neglecting current control loops and the dynamics of grid inductors will moderately decrease the accuracy of the model. Finally, time-domain simulations have confirmed the validity of the proposed several large signal models.