With the increasing proportion of new energy connected to the grid

the issue of frequency safety in the power system and mastering the regulation ability of the units have become more important. At present

in power system simulation

thermal power unit models suitable for electromechanical transient and medium-long term dynamics mainly adopt the simplified model of drum boilers and the single reheater turbine model recommended by IEEE. If a similar model is also used for the once-through boiler unit

the simulation results of the main steam pressure will deviate significantly from the actual situation due to the dynamic of thermal storage coefficient and the deviation of control system

which leads to a misjudgement of the unit's regulation ability. By using thermodynamic modeling methods

a supercritical once-through boiler unit model suitable for multi-time scale dynamic simulation is proposed. By establishing a moving boundary model of the water wall and a dynamic heat flow model of the superheater

the heat storage capacity of the once-through boiler can be reflected more accurately. By incorporating feedwater control and superheat control

the control system is more in line with the actual unit. The high simulation accuracy of the model is verified using power plant operation data. Compared with the existing power simulation models

the simulation accuracy of the main steam pressure has been improved significantly. Therefore

the model can describe the dynamics of supercritical once-through boiler units more accurately in primary and secondary frequency regulation and peak shaving

which is helpful for simulating the frequency process of power systems.