Transient Stability Analysis for Grid-Forming Energy Storage Systems with Current Limit

Grid-Forming Energy Storage Systems are key sources to help stabilize the new power system, which are connected to the grid through Grid-Forming Convertor (GFMs). Due to the low overcurrent capability of the power electronics devices, GFM often have current limiting loops, which may significantly alter the transient synchronous stability of GFMs. This paper establishes a single GFM system and focuses on the impact of the current limit on the transient stability of the system. In addition, the critical stability conditions of GFM subjected to permanent and non-permanent active power step disturbances are examined using the equal area criterion. The results provide the critical active power step values and the corresponding critical power recovery angles. Finally, time-domain simulations were conducted to validate the theoretical analysis, and the study revealed that the current limit significantly reduces the transient stability margin of grid-forming converters.