摘要
乙烯裂解炉炉管出口温度控制系统中存在着多变量耦合情况,导致在实际生产中很难实现对各组炉管温度的精确控制。针对这种情况,本文提出了一种基于可逆解耦策略和内模PID控制原理的多变量控制系统设计方案。文中首先介绍乙烯裂解炉的结构,并对其工作原理和生产的工艺流程作了简单说明;其次根据现场得到的数据并进行滤波,去趋势项等处理,运用预报误差算法(PEM)进行系统辨识,建立了过程的多变量输入输出模型;再次,介绍了可逆解耦方法的基本原理和实现过程,并针对辨识得到的模型,采用该方法设计系统的解耦环节。它可以避免采用传统解耦方法时的复杂运算过程,能够较为快捷地得到解耦参数矩阵。最后,针对解耦后的被控系统设计控制器。由于内模控制具有结构简单,控制性能良好等特点,本文中采用内模控制原理设计带滤波器形式的PID控制器,并给出了滤波系数等相关参数值。同时,对模型存在失配的情况和模型匹配时采用传统单回路控制策略的情况,以及不对系统解耦而直接设计PID控制器进行控制的情况分别进行仿真,并比较了仿真结果。分析表明,系统解耦后,对其控制时的静态误差消除时间大大缩短,动态性能得到改善,从而实现了对裂解炉炉管出口温度快速准确控制的要求,说明了该方案的有效性。
Multivariable coupling exists in the control system of the coil out temperature （COT） in the ethylene cracking furnace, which lets it hard to achieve accurate control over the temperature of the furnace in actual production. To solve this problem, a multivariable control system based on inverted decoupling strategy and IMC-PID was proposed in this paper. Firstly a brief introduction about the structure of ethylene cracking furnace and its operating principle, together with its working flows is made. And secondly, the model of the real process is established. In order to get it, we handle the data obtained from real production with filtering and removing the trend term and adopting the Predictive Error Method （PEM） to make the identification of the system. Then a multi-input and multi-output model is obtained. Thirdly, we adopt the principle of the inverted decoupling method and its design procedure-according to which, the decoupling structure can be determined for the model got from identification. This method can avoid the complex computations occurred when using the traditional decoupling approaches, and deduce the decoupling matrix quickly. Finally, controllers are designed for the decoupled system. Because the Internal Model Control （IMC） is featured as simple-structure and good control performance, we design the PID controller with a filter based on it. And the relative parameters, such as the coefficients of the filter, are given. In the following three cases, model mismatches and controlled by the proposed method, the conventional single loop control strategy and the IMC-PID controller without deeoupling, the simulation results are given. The comparison of the simulation results suggest that the time for erasing the static error can be shortened significantly and the dynamic performance of the system can be improved a lot after it is decoupled using the proposed method. It can fulfill the requirement of ethylene cracking furnace for a fast and accurate control on the COT, and therefore the method is effective.
出处
《计算机与应用化学》
CAS
CSCD
北大核心
2012年第1期90-94,共5页
Computers and Applied Chemistry
基金
国家863重点项目课题(2007AA041402)
上海市重点学科建设项目资助(B504)
关键词
裂解炉
多变量系统辨识
系统解耦
IMC-PID
cracking furnace
identification of multivariable system
system decoupling
IMC-PID
