The Star-Connected Cascaded H-Bridge STATCOM (CHB STATCOM) is widely utilized for reactive power compensation in medium and high voltage grids. However, with the increasing penetration of power electronic devices in modern power grids, the requirements for STATCOM during Low-Voltage Ride-Through (LVRT) have become more stringent. Currently, many power grid standards demand that distributed grid-connected power generation systems operate at certain voltage drops and inject additional reactive current to support grid voltage sag recovery. As a result, accurately portraying the output limit of STATCOM reactive current during faults has become a significant research topic in both academia and industry. This digest considers the influencing factors such as control methods, fault scenarios, equipment scenarios, etc., while quantitatively analysing the STATCOM reactive current limits under three asymmetrical grid faults. Finally, the correctness of the analysis is verified by simulation.