Urea-SCR系统尿素喷射数据驱动预测控制研究

摘要

Urea selective catalytic reduction (urea-SCR) systems are well known for exhaust gas aftertreatment in power plant applications.Stringent specifications and the dynamic operation mode of such applications demand advanced control strategies.The control purpose of urea-SCR is to simultaneously achieve high NOx conversion efficiency and low ammonia slip.The two emission demands are contradictory.Moreover,owing to the dynamic operation mode of urea-SCR systems,advanced control strategies are required to improve urea injection control.A data-driven predictive controller for urea injection was designed.The input-output data were directly obtained from ETC driving cycle test of the diesel engine bench.The controller was derived by the coupling excitation and separation of the data.Because of the physical characteristics,the input and output constraints were considered explicitly in the problem formulation.In order to obtain offset-free control for the reference input,the predictor equation was gained with incremental inputs and outputs.The experimental test was carried out in ETC and other transient test cycle.The results showed that the controller was able to meet emission control requirements under the excitation test cycle.The closed-loop system had the ability to reject uncertainties caused by uncertainty of working conditions under the non-excitation test cycle.%为了同时实现较高的NOx转化效率和较低的NH3逃逸量这一矛盾的排放控制需求,基于数据驱动预测控制技术设计了一款urea-SCR系统尿素喷射控制器.数据来自某型号柴油机台架ETC瞬态循环测试试验,控制器直接由四输入及两输出(预测输出和约束输出)耦合激励再分离得出.基于系统的实际物理特性,在控制问题描述中明确考虑了输入输出量的时域约束.考虑到相对参考无偏的控制需求,预测方程采用增量型.台架测试表明,激励工况下,控制器能够满足优化问题提出的排放控制目标;非激励瞬态工况下,对于工况变化不确定性引起的干扰,控制器具有较好的鲁棒性.