Selective catalytic reduction (SCR) denitration system and method based on constraint predictive control

The invention discloses a selective catalytic reduction (SCR) denitration system and method based on constraint predictive control. The flow of injected ammonia of the SCR denitration system is controlled by utilizing a predicting-proportioning cascade control policy; the flow of the injected ammonia is regulated by predicting the future change tendency of the concentration of NOx at an outlet of an SCR reactor and regulating the opening degree of an ammonia injection valve in advance; therefore, the defects of large inertia and delay of the SCR denitration system can be greatly overcome, the response speed of ammonia injection amount control to unit load change is increased, and the dynamic regulation quality of the SCR denitration system is improved; under the constraint predictive control, practical constrains, such as upper and lower constrains of valve opening degree, valve operation speed constrain and outlet NOx concentration constrain, are simultaneously considered and are used in parallel, so that the fact that the system performance is influenced due to saturation of execution mechanisms is avoided; based on ensuring the fact that the concentration of the NOx at the outlet reaches a target value, the ammonia injection amount is reduced as much as possible, and the operation cost and the ammonia escape rate are effectively reduced.