Abstract: This paper analyzes the reasons on the failure of forced convertor of SFC in the pumping storage condition in Inner Mongolia Hohhot Pumped-Storage Power Station. By studying on the flux linkage equation of the rotor initial position detection, the pumped-storage unit monitoring system, SFC and the excitation system are coordinated to improve the success rate of the unit from the static condition to the pumped phase modulation. A kind of differential protection for SFC that can effectively reduce the misoperation rate of the relaying is proposed.