CC Function Block Configuration
Starting with the default configuration, configure the following parameters:
Parameter | Description |
PVEUMax | Maximum scaled value for PV. |
PVEUMin | Minimum scaled value for PV. |
SPHLimit | SP high limit value, scaled in PV units. |
PPLLimit | SP low limit value, scaled in PV units. |
CV1InitValue | An initial value of the control variable CV1 output. |
CV2InitValue | An initial value of the control variable CV2 output. |
CV3InitValue | An initial value of the control variable CV3 output. |
If you have the process models available, you can intuitively tune the CC control variable by entering the following parameters:
Parameter | Description |
ModelGains | Nonzero numbers (negative for direct acting control variable, positive for reverse acting control variable) |
ModelTimeConstants | Always positive numbers |
ModelDeadtimes | Always positive numbers |
ResponseTimeConstants | Always positive numbers |
Active 1st, 2nd and 3rd CV | Specify the order in which CV's will be used to compensate for PV - SP error. |
Target 1st, 2nd and 3rd CV | Specify the priorities in which CV's will be driven to their respective target values. |
CVTargetValues | Specify to which values should the control variable drive the individual CV's |
TargetRespTC | Specify the speed of CV's to approach the target values |
The function block behaves in a defined way for any combination of CV Active and Target lists and CV Auto-Manual modes. The function block attempts to accomplish these goals in the following order of priorities:
- Control PV to SP
- Control Target1stCV to its target value
- Control Target2ndCV to its target value
If any CV is put in Manual mode, the CC function block gives up the goal with priority 3. If two CV's are in Manual mode, the CC function block is reduced to an IMC, (single input, single output) control variable controlling the PV to its setpoint.
In addition to this, however, the control variable reads the Manual CV values from the CV's that are in Manual mode as feedforward signals. Then, the CC function block predicts the influence of the Manual CV values on the PV by using the appropriate internal models, and calculates the third CV that remains in Auto mode.
For integrating process types (such as level control and position control), internal nonintegrating models are used to approximate the integrating process. The Factor parameter is used to convert the identified integrating process models to nonintegrating internal models used for CV calculation. This is necessary to provide for stable function block execution.
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