External power grid fault will affect the operation of nuclear power units. It is of great practical value to establish a suitable simulation model of nuclear power unit to study the interaction between power grid and nuclear power units. Based on the equivalent modeling method

the whole model of M310 reactor unit is established

and according to the sensitivity of coolant main pump to the change of power grid frequency

the power grid fault interface is introduced into the main pump model. The effectiveness of the overall model of the unit is verified by comparing with the working conditions in design manual. Combined with the power grid protection measures of the unit

simulation on the influence of low frequency fault on the unit operation is carried out. The results show that

when a low frequency fault occurs in the power grid with slow frequency reduction rate

the influence of the fault on thermal parameters of the reactor core is obvious. However

under the operation safety protection measures of the unit

there will be no harm to the unit operation safety.