The control activities and response characteristics of UHVDC projects subjecting to AC system faults at the rectifier side are studied, considering the effect of Rectifier Alpha Minimum Limiter link (RAML). First, an HVDC system model which has the same control logic as that used in a real UHVDC system is built in PSCAD/EMTDC. Based on this model, the effect of RAML on the dynamic responses of the rectifier side during transient process of the system is investigated. The analysis results show that, with RAML, the overshoot of the DC voltage and DC current is avoided. However, the recovery speed of the DC voltage, DC current as well as the active power delivered by the HVDC link is slowed down. Furthermore, with RAML, the converters will consume more reactive power. Second, the effect of RAML on the angle stability of the AC system at the sending end is analyzed based on EEAC theory, and the analysis results are verified by simulations on Sichuan power system. This work is supported by Sichuan Science & Technology Department Major Research Development Project (No. 2017GZ0054) and China Postdoctoral Science Foundation (No. 2015M582543).