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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。
Ethylene cracking furnace tube outlet temperature control system exists multivariable coupling conditions, resulting in the actual production is difficult to achieve precise control of the temperature of each tube. In view of this situation, this paper presents a multi-variable control system design based on reversible decoupling strategy and the internal model PID control principle. In this paper, the structure of the ethylene cracking furnace is introduced first, and its working principle and production process are described briefly. Secondly, based on the data obtained from the field and the filtering and de-trending terms, the system is identified by using the prediction error algorithm (PEM) , And establishes a multivariable input-output model of the process. Thirdly, the basic principle and implementation process of the reversible decoupling method are introduced. According to the identified model, the decoupling of the system is designed. It can avoid the complicated operation process when adopting the traditional decoupling method and can obtain the decoupling parameter matrix more quickly. Finally, the controller is designed for the decoupled controlled system. Due to its simple structure and good control performance, the internal model control is designed in this paper. The internal model control principle is used to design the PID controller with filter, and the relevant parameters such as the filter coefficient are given. At the same time, the simulation results of the model are given when the model is mismatched and the traditional single-loop control strategy is adopted when the model is matched, and the PID controller is designed without decoupling the system. The analysis shows that after the system is decoupled, the elimination time of static error is greatly shortened and the dynamic performance is improved. The requirement of fast and accurate control of outlet temperature of cracking furnace tube is realized, and the effectiveness of the scheme is proved.