Fault Modeling of Grid-forming Converters using Dynamic Phasor Theory

It has been pointed out in recent years that grid-following and grid-supporting converters are harmful to the stability of the power system, and grid-forming converters (GFM) are becoming to be the most promising grid-connected converters for the integration of renewable energy. Nevertheless, the development of GFM converters challenges the fault analysis of the power system because GFM converters have a totally different fault response with that of the grid-supporting, grid-following converter, and the synchronous generator. The fault modeling of GFM converters is a foundation to overcome this issue, so it should be investigated firstly. However, this topic is rarely discussed in the previous literature. In order to fill this research gap, this paper proposes a fault modelling method for GFM converters based on the dynamic phasor theory. The dynamic phasor model of GFM converters can provide an effective interface to the power system analysis. Thus, the proposed model is outstanding because of its ability to analyze the interaction between converters and the power system in the fault analysis. To verify the correctness of the proposed model, a 12 MVA grid-forming converter is established in MATLAB/Simulink. The simulation results show that the proposed model can almost perfectly handle the fault analysis of the grid-forming converter.