優(yōu)化 – 理解主控制器的經(jīng)濟優(yōu)化功能，以最具成本效益的方式運行流程，同時達到設(shè)定點或者最大限度地減少能耗/最大限度地提高產(chǎn)品收率等是非常重要的?；趥€人成本的經(jīng)濟系數(shù)可以分配諸如能源成本或進料最大化等因素來實現(xiàn)最佳的經(jīng)濟效益。
在許多應(yīng)用中，要求不能通過使用子控制器可用的所有自由度將所有變量保持在約束內(nèi)控制。人們可以通過經(jīng)濟目標(biāo)函數(shù)來使用額外的自由度，以便控制器除了控制之外經(jīng)濟地優(yōu)化工藝。
經(jīng)濟函數(shù)是控制器最小化的雙線性函數(shù)。它由操作輸入和測量輸出變量的雙線性組合組成。經(jīng)濟系數(shù)出現(xiàn)在雙線性組合中。
可以定義多個經(jīng)濟函數(shù)，但一次只能有一個經(jīng)濟函數(shù)活躍?？梢栽诰€選擇活躍經(jīng)濟函數(shù)。經(jīng)濟系數(shù)也可以在線更改。
被控變量始終優(yōu)先于經(jīng)濟函數(shù)。
為了實現(xiàn)經(jīng)濟優(yōu)化過程，Exasmoc控制器允許用戶定義經(jīng)濟函數(shù)。
控制目標(biāo)：
? 將C5的丁烷保持在設(shè)定點；
? 保證塔盤在整流部分不液泛淹塔；
? 將再沸器保持在最小負荷以上。
經(jīng)濟目標(biāo)：
? 最小化塔壓（分離效率）；
? 最大化FCU MCR排熱量（增加進氣量.....）
? 嘗試實現(xiàn)經(jīng)濟與調(diào)度部門設(shè)定的目標(biāo)RVP。
A2.3 Exasmoc控制器操作模式
主控制器
? OFF
Exasmoc多變量，模型預(yù)測和優(yōu)化函數(shù)為OFF。用戶嘗試使用基于DCS的BRC和ERC功能來穩(wěn)定流程。
? STANDBY
Exasmoc處于待機模式（計算但不提供輸出）。
使用基于DCS的BRC和ERC功能來穩(wěn)定流程。用戶正在觀察Exasmoc standby操作，以便可以將以下模式投用。
? CONTROL
Exasmoc處于多變量模型預(yù)測控制模式下，并在設(shè)定點或指定設(shè)定范圍內(nèi)嚴(yán)格控制CV，同時在定義的約束內(nèi)保持其他參數(shù)。基于DCS的BRC和ERC也在DCS PID等遠程模式下接受來自Exasmoc的MV。
? OPTIMISE
Exasmoc處于多變量模型預(yù)測和優(yōu)化控制模式下，在嚴(yán)格控制CV和其他控制目標(biāo)的前提下，還追求經(jīng)濟有效的穩(wěn)態(tài)運行模式?；贒CS的BRC和ERC在運行，且DCS PID等在遠程模式下接受來自Exasmoc的MV值?？梢詾閭€人經(jīng)濟函數(shù)指定成本/收益部分，以實現(xiàn)優(yōu)化的最大經(jīng)濟效益。
原文：
Optimisation – It is important to understand economic optimization function of the main controller in order to run the process at most cost effective way while achieving the set point or the desire to minimize/maximize energy consumption, product yield etc. Economic Coefficients based on individual cost factor such as cost of Energy or the Feed maximization can be assigned to achieve most optimum economic benefits.
In many applications, the control requirement to keep all variables inside the constraints does not use all the degrees of freedom available to sub-controllers. One can use the extra degrees of freedom by means of economic objective function so that the controller optimizes the process economically in addition to controlling it.
The economic function in is a bilinear function that the controller minimizes. It is made up of terms that are bilinear combinations of manipulated input and measured output variables. Economic coefficients appear in the bilinear combinations.
Multiple economic functions can be defined, but only a single economic function can be active at a time. The active economic function is selected on-line. The economic coefficients can also be changed on-line.
Controlled Variables have always a higher priority than Economic Function.
In order to achieve economic optimization of the process, Exasmoc controller allows user to define Economic Function.
Control Objectives:
? Keep C5 in Butane at setpoint
? Keep tray loading in rectifying section < flooding
? Keep reboiler above min load
Economic Objectives:
? Minimise column pressure (separation efficiency)
? Maximum heat removal from FCU MCR (increase crude intake .....)
? Try to achieve target RVP set by Economic & Scheduling dept.
A2.3 Exasmoc Controller modes of operation
Main Controller
? OFF
Exasmoc Multivariable, Model Predictive and Optimization function is OFF. User trying to stabilize process using DCS based BRC and ERC function.
? STANDBY
Exasmoc in a stand by mode (Computing but not providing outputs)
DCS based BRC and ERC function stabilizes the process. User is observing Exasmoc standby actions so that following mode can be put on line.
? CONTROL
Exasmoc in a Multivariable Model Predictive Control mode and tightly controlling CV at set point or within specified set range while maintaining other parameters within defined constraints. DCS based BRC and ERC in operation also DCS PID’s etc in a remote mode to accept MV’s from Exasmoc.
? OPTIMISE
Exasmoc in a Multivariable Model Predictive and Optimizing Control mode and tightly controlling CV’s and other control objectives in addition to cost effective steady state operation. DCS based BRC and ERC in operation, also DCS PID’s etc in a remote mode to accept values of MV’s from Exasmoc. It is possible to assign cost/benefits constituents for individual Economic Function to achieve Maximum Economic benefits from Optimization.
2017.3.26
