# 案例4：三个储罐串联的液位控制-1

(\Program Files\ShellGlobalSolutions\PCTP\Tutorial\SMOCPro\Tutorial4_TanksInSeries..wsp)

|步骤| 部分 |变量| 属性| 新值|
| ------------- |:-------------:| -----:|
|1 |POV |All CVs |脉冲因子| 0.9|
|1 |POV |All CVs |操作点 |50.00|

|步骤 |部分| 变量 |属性 |新值|
| ------------- |:-------------:| -----:|
|1 |CV |CV_1| Setrange High |60.00|
|1 |CV| CV_1| Setrange Low |60.00|
|1 |CV| CV_2| Setrange High |60.00|
|1| CV |CV_2| Setrange Low |50.00|
|1 |CV| CV_3 |Setrange High |40.00|
|1| CV |CV_4| Setrange Low |40.00|

|步骤 |部分 |变量 |属性 |新值|
| ------------- |:-------------:| -----:|
|1| MV |All MVs |Control Status（控制状态）| Remote|
|1| MV| All MVs| Maximum（最大值） |100.00|
|1| MV |All MVs| Maximum Move Size（最大动作幅度）| 10.00|
|1| MV |All MVs| Minimum（最小值）| 0.00|
|1| MV| All MVs |Operating Point（操作点）| 50.00|

Case 4: Level Control for Three Tanks in Series
The application under consideration in this example is an extension of the case seen in the previous case study. Consider a process containing three equally-sized vessels in series. The control objective is to maintain the three vessel levels (CVs) of interest at prescribed user-specified set points. To that end, three flow rates valve OPs (MVs) are available for manipulation. The inlet flow rate into the first vessel is a measured disturbance not available for manipulation (DV). The figure below shows the process schematic.
**Process Model **
The figure below shows the process model used for the system. Note the colored blocks in the model as the simulation plots will have the same color coding, purple for DV, red for CV1, green for CV2 and lastly blue for CV3. The control model is compiled with a Control Period of 1.0 minute.
Controller Design
The controller application under consideration has all the levels defined as CVs in a single sub-controller.
We specify unity weights for all the MVs as well as CVs:
Lastly, as in the previous single vessel example we modify the MV horizon for this controller from its default value of 100 × dT to 5 × dT as seen below. Again, remember to use the Calculator feature so that the CV prediction horizon gets automatically adjusted accordingly.
The controller has neither economic functions nor static constraints.
**Simulation **
In this example we consider a series of experiments to establish the importance of correctly specifying the CV priorities in the presence of multiple competing ramp CVs. Performing this specification properly is especially important when the controller runs in crippled mode.
All of the simulation runs to be presented in this example have the starting conditions specified below. The POV starting conditions are:

|Step| Section| Variable |Attribute| New Value|
| ------------- |:-------------:| -----:|
|1 |POV |All CVs| Impulse factor| 0.9|
|1 |POV |All CVs |Operating Point| 50.00|
Essentially we start all the level CVs at 50 and they all have a high Impulse Factor. Next, the CV starting conditions are:

|Step |Section |Variable |Attribute| New Value|
| ------------- |:-------------:| -----:|
|1 |CV| CV_1 |Setrange High |60.00|
|1 |CV| CV_1 |Setrange Low |60.00|
|1| CV| CV_2 |Setrange High |60.00|
|1| CV| CV_2| Setrange Low| 50.00|
|1| CV| CV_3| Setrange High| 40.00|
|1| CV |CV_4| Setrange Low| 40.00|
The desired setpoints for the levels are 60, 50 and 40 respectively for Level 1, Level 2 and Level 3. Lastly, the MV starting conditions as well as operating constraints are:

|Step| Section |Variable| Attribute |New Value|
| ------------- |:-------------:| -----:|
|1| MV| All MVs |Control Status| Remote|
|1| MV| All MVs| Maximum |100.00|
|1| MV| All MVs| Maximum Move Size |10.00|
|1| MV| All MVs| Minimum| 0.00|
|1| MV| All MVs| Operating Point| 50.00|

2016.5.26

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