Fast Active Power Recovery for Grid-Forming Converter During Postfault Under Different R/X Ratios of Grid Impedance

Abstract

Fast active power recovery is very important for grid forming (GFM) converters to support the grid after clearing faults. However, most existing research only focuses on the voltage sag process without much attention paid to the postfault process. This article first reveals that the active power recovery of GFM converter at postfault stage is affected by the resistance inductance ratio (R/X ratio) of the grid impedance. It is found that the power angle would shift a lot during grid faults with a large R/X ratio, which causes power oscillations of GFM when the grid voltage is restored to the rated value. After revealing the influence of GFM control parameters on dynamic performance at the postfault stage, this article proposes a fast compensation method of power angle. This method can shorten the transient process of GFM converters and suppress possible instabilities during the postfault stage. Theoretical analysis and experimental verification show that the proposed method has wide applicability under different grid impedances.