After high voltage direct current(HVDC)is blocked

frequency deviation and power translation will emerge in the receiving-end of hybrid AC/DC system. Such accidents as under-frequency load shedding and branch violation would become more serious. For the purpose of solving the above problems

a unit commitment model is proposed for receiving-end power grid in the hybrid AC/DC system

including capacity constraints on primary frequency regulation and bus voltage/branch power constraints when secondary frequency regulation finishes. As a result

frequency and power flow would be ensured while HVDC blocked failure happens. According to the characteristics of the model

Benders decomposition and mixed integer programming algorithms are used to get the optimal transmission power of HVDC and planning of normal units. HVDC power will be completely accommodated while AC/DC system safety will be ensured. In the end

two typical cases of 10-machine 39-node system and Jiangsu power grid are employed to test the correctness and effectiveness of the model.