In view of the limitation of conventional model identification method and the difficulty of controller parameter optimization caused by the large delay

inertia and nonlinearity of NO_x mass concentration at outlet of SCR denitrification system of coal-fired unit

this paper analyzes the structure of SCR denitration control system of a supercritical 660 MW unit

excavates the operation data at different historical loads

adopts the closed-loop identification method

uses particle swarm optimization algorithm to optimize the model parameters

and establishes the transfer functions of SCR denitration system regulating valve opening and ammonia flow object

ammonia flow and outlet NO_x mass concentration object

flue gas flow and outlet NO_x mass concentration object. The simulation results of model identification based on MATLAB show that

the identification curve can better reflect the actual output curve

and the simulation results verify the effectiveness and reliability of the method.