This paper analyzes the effect of grid-following (GFL) converter on transient stability of grid-forming (GFM) converter in a paralleled GFM-GFL converter system. A unified power-angle dynamic model is derived for the system. The model reveals that a slower phase-locked loop reduces the angle-tracking capability of the GFL converter, resulting in a larger power derivation. This derivation is equivalent to a drop in power reference of GFM converter, which enhances the transient stability when the power angle increases, but degrades the transient stability when the power angle decreases. These findings are validated through experimental tests.
.jpg "Haowen Wang, ME (he/him/his) photo")
