Modelling and Analysis of Damping Characteristics of Grid Following Converter

The synchronization instability is one of the main issues for the operation of grid-following converter (GFL). Analogizing to the synchronous generator mechanism, GFL synchronism can be modelled in the form of swing equation. Thus, under the assumption that the damping is negligible, the equal area criterion (EAC) method is used to determine the GFL synchronization stability. However, in practice the damping is significant and inconstant during the transients. Sometimes, the damping becomes negative during the transients even is positive in the pre-fault, and resulting in the instability. The effect of the damping on the synchronization stability has not been thoroughly investigated. This paper visually reveals this effect. The simulation results show that the negative damping of GFL may lead to an optimistic prediction of synchronization stability by EAC method.