To meet the demands of power grid stability analysis in medium and long-term period

a new nonlinear mathematical model with linear transfer function form for(ultra)supercritical boilers was built.Both steady and dynamic nonlinear characteristics were considered to make the model parameters that can accurately reflect the practical boiler's load response characteristics be easy to be obtained through disturbance tests.Moreover

taking a supercritical 600 MW unit as an example

the particle swarm optimization(PSO)algorithm based parameter identification method was employed to identify parameters of the nonlinear mathematical model.The results show that

the nonlinear function in nonlinear model of the(ultra)supercritical boilers can be obtained by model parameter identification at each load point.The large the load point number

the smoother the nonlinear function curve and the better the nonlinear fitting effect.The simulation results of the identified model were in accordance with the test output

indicating the proposed model and its parameter identification method are feasible.