Abstract: In view of the non-linearity, time-varying and large delay characteristics of SCR flue gas denitrification system, a multi-model switching DMC-PID cascade predictive control method for variable conditions operation is proposed under the background of coal-fired units participating in deep peak shaving. Firstly, the local linear model of SCR denitrification system under different working conditions is established by using system identification method. Secondly, the parameters of DMC-PID controller are designed according to the principle of quadratic optimal control. Finally, the switching conditions are designed according to the unit load instructions, and the DMC-PID cascade predictive control of denitrification system under variable conditions is realized by using multi-mode switching control method. The results show that compared with DMC-PID cascade predictive control without switching control and cascade PID multi-mode switching control with switching control, the multi-mode switching DMC-PID cascade predictive control designed in this paper has the advantages of small output fluctuation, small overshoot, short adjustment time, rapid response, strong anti-interference ability and good robustness under variable operating conditions, and is suitable for industrial process control with non-linearity, time-varying, large delay and variable operating conditions.

Key words: SCR flue gas denitrification, multi-mode switching, dynamic matrix control(DMC), cascade predictive control, variable conditions

摘要： 在当前燃煤机组参与深度调峰的背景下，针对SCR烟气脱硝系统的非线性、时变性与大迟延特性，提出一种用于变工况运行的多模切换DMC-PID串级预测控制方法。首先采用系统辨识方法建立不同工况下SCR脱硝系统的局部线性模型；其次依据二次最优控制原理设计各工况点的DMC-PID控制器参数；最后根据机组负荷指令设计切换条件，通过多模切换控制方法实现脱硝系统在变工况时的DMC-PID串级预测控制。研究结果表明，与未采用切换控制的DMC-PID串级预测控制和采用了切换控制的串级PID多模切换控制相比，在机组变工况运行时，多模切换DMC-PID串级预测控制具有变工况输出波动小、超调量小、调节时间短、快速性好、抗干扰能力强、鲁棒性好等优点，适用于具有非线性、时变性、大迟延特性以及变工况运行的工业过程控制。

关键词: SCR烟气脱硝, 多模切换, 动态矩阵控制, 串级预测控制, 变工况