换热网络闭环柔性控制与优化研究

STUDY ON CLOSED-LOOP FLEXIBLE CONTROL AND OPTIMIZATION OF HEAT EXCHANGER NETWORK

通过换热器旁路调节,可以有效提高换热网络柔性和控制系统的冗余量,有利于构成换热终温的闭环控制,进而提高换热网络工作品质和系统工作的稳定性。同时,换热网络温度闭环控制是典型的多入多出(MIMO,Multiple Input Multiple Output)系统,各控制回路之间存在严重耦合,相互影响,严重制约了系统控制品质和操作弹性,对控制系统参数整定造成极大困难。通过换热网络灵敏度分析进行调节变量和被控变量的匹配设计,从换热网络自身的运行特性和控制回路耦合关系的定性分析对配对关系进行筛选,可以在工程设计阶段有效降低各控制回路之间的耦合度,提出共振型耦合的概念和判别方法,用于优化控制回路变量配对设计过程,补充和完善了换热网络调节变量选取和配对规则,为换热网络的旁路优化控制设计提供了一种有效的思路。

By adjusting the by-pass of heat exchanger,the flexibility and the control system redundancy of heat exchanger network can be improved effectively,which is beneficial to form the closed-loop control of the final heat transfer temperature,thus the working quality of the heat exchange network and the working stability of the system can be improved.The temperature closed-loop control of the heat exchanger network is a typical multi-input,multi-output(MIMO)system,there are serious coupling and mutual influence among the control loops,the control quality and operation flexibility of the system can be restricted seriously,which make it difficult to control system set-up and parameter settings.The sensitivity analysis of heat exchanger network is used to adjust the matching design between adjusting variables and controlled variables.The matching relationship is selected effectively through the qualitative analysis of operating characteristics and coupling relationship of control loops,which reduces the coupling degree between the control loops effectively in the engineering design stage.The concepts and discrimination methods of resonance coupling are proposed,the design process of control loop variable matching is optimized,and the selection and matching rules of adjusting variables are supplemented and perfected.It provides an effective method for the optimization of by-pass control of heat exchanger network.