帶回家的消息
當(dāng)遇到斜坡CVs時(shí)，CV優(yōu)先級(jí)的概念和它的正確實(shí)施是非常重要的。用戶以這種方式指定斜坡CV的優(yōu)先級(jí)時(shí)必須小心，對(duì)每個(gè)應(yīng)用基礎(chǔ)如果遇到競(jìng)爭(zhēng)的控制目標(biāo)和/或殘缺模式時(shí)，確保控制行為仍是需要的行為。對(duì)穩(wěn)定斜坡CVs，在通過(guò)設(shè)定優(yōu)先級(jí)完全相同將它們指定為同樣重要的情況下，由于穩(wěn)態(tài)約束的存在，斜坡CV對(duì)可到達(dá)目標(biāo)計(jì)算依舊有較強(qiáng)的貢獻(xiàn)。
**Take Home Message **
The CV priority concept and its correct implementation when it comes to ramp CVs is extremely important. The user must take care in specifying ramp CV priorities in such a way that if either competing control objectives and/or crippled mode are encountered then the control behavior will be the desired behavior on a per application basis. In the cases where stable and ramp CVs are specified to be of the same importance by setting their Priorities identical the ramp CV will still have a stronger contribution to the reachable target calculation due to the stabilization constraint.
案例6：加氫脫硫（HDS）和進(jìn)料混合控制
(\Program Files\ShellGlobalSolutions\PCTP\Tutorial\SMOCPro\Tutorial6_HDSandFeed.wsp)
接下來(lái)我們提出了一個(gè)加氫脫硫（HDS）控制方案的例子。這里主要有兩個(gè)目的：
1.為了說(shuō)明子控制器的概念；
2.為了說(shuō)明如何使用混合（多個(gè)）子控制器
過(guò)程模型
該過(guò)程描述由下圖總結(jié)。
汽油的Sulphur（硫分）、T95和Density（密度）都從HDS反應(yīng)器下游測(cè)量。問(wèn)題是要將這些指標(biāo)控制在各自的特定高限下面。操作變量是Kero（煤油），LGO和HGO的混合比，整體的進(jìn)料流量和爐出口溫度。
我們也將進(jìn)料或利潤(rùn)范圍最大化（優(yōu)化）設(shè)定為經(jīng)濟(jì)函數(shù)。CGO比率的影響被建模并用作進(jìn)料前饋干擾。
模型搭建
我們的目標(biāo)是使用此策略搭建并調(diào)諧一個(gè)SMOCPro控制器。如下所示，在圖形化模型構(gòu)造器(GMB)中展現(xiàn)了過(guò)程模型。
傳遞功能塊右上角的紅色三角形表示Kero, LGO,HGO,CGO的比例增益是可以修改的。這一特性允許處理不同的進(jìn)料類型。
從圖中我們?nèi)菀追謩e描繪混合加氫脫硫（HDS）反應(yīng)器的子單元。因此我們使用此模型來(lái)說(shuō)明子系統(tǒng)的概念。我們的意向是建立兩個(gè)子系統(tǒng)，即一個(gè)用于攪拌器，另一個(gè)用于HDS反應(yīng)器?！癝ULPHUR_IN”和“Dyn_SulfInToSulf”對(duì)應(yīng)于子系統(tǒng)間的連接。
若要開(kāi)始此流程，首先選擇與攪拌器子模型相關(guān)聯(lián)的所有塊。選擇完成后，在某一選中的塊上右鍵鼠標(biāo)按鈕并選擇Create SubSystem（創(chuàng)建子系統(tǒng)）。
選中的塊被一可重命名為“BLENDER”的子系統(tǒng)塊所代替。類似地，可在剩余的視圖塊創(chuàng)建“HDS”子系統(tǒng)（適當(dāng)?shù)刂孛螅?/p>
原文：
**Case 6: Hydro-desulphurization (HDS) and Feed Blending Control **
(\Program Files\ShellGlobalSolutions\PCTP\Tutorial\SMOCPro\Tutorial6_HDSandFeed.wsp)
Next we present an example of a Hydro-Desulphurization (HDS) control scheme. Here, there are two main objectives:
- To demonstrate the sub-controller concept
- To demonstrate the use of blending (multiple) sub-controllers
**Process Model **
The process description is summarized by the figure below.
The gasoil Sulphur, T95 and Density are measured downstream from the HDS reactor. The problem is to control these qualities below their specific high limits. The manipulated variables are the Kero, LGO and HGO feed blending ratios, the overall Feed flow and the furnace outlet Temperature.
There is also a scope for Feed or Profit maximization (optimization) to be set as an economic function. The influence of the CGO ratio is modeled and used as a feed forward disturbance.
Model Building
The objective is to build and tune a SMOCPro controller using this strategy. The model for this process appears in the Graphical Model Builder (GMB) window shown below.
The top right red triangle in the transfer function blocks indicates that the gains for Kero, LGO, HGO and CGO are ratios that can be modified. This characteristic allows for processing of different Feed types.
From the figure, it is easy to delineate the blending and the HDS reactor sub-units, respectively. Thus, we use this model to illustrate the sub-system concept. The intent is to create two sub-systems, i.e. one for the blender and the other for the HDS reactor. The “SULPHUR_IN” to “Dyn_SulfInToSulf” corresponds to the link between the sub-systems.
To begin the process, first select all the blocks associated with the blender sub-model. After the selection has been done, right click the mouse button on one of the selected blocks and select Create SubSystem.
The selected blocks are replaced by a sub-system block that can be renamed “BLENDER”. Similarly, an “HDS” sub-system (after appropriately renaming it) can be created with the remaining blocks of the view.
2016.6.9
