Wrong ET Calculation when EPSMVPMX solution 2 on a DMC3 controller
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Products:
Aspen DMC3
Last Updated:
19-Apr-2021
Last Updated:
19-Apr-2021
Versions:
Article ID:
000098364
Article ID:
000098364
Primary Subject:
Problem Statement
The current solution described a strange behavior that can be encountered on a DMC3 controller.
If you have an MV with an ET target and you change one of the limits to something outside the current value, the SS Target takes a big jump and calculates a value equal to twice the limit.
Solution
In the next example, the Low Limit for the MV is at 0. The SS Target and the Current Value is around the same value. The ET Service Switch is OFF and the Controller behaves as expected after the low limit changes from 0 to 10:
But if the ET Service Switch is ON, and the same changes are made, the SS Target is calculated to be twice the value of the limit:
This problem can be solved by changing the parameter for TargetAlgorithmType (EPSMVPMX) from 2 to 4
2 -
Legacy interior point QP algorithm
4 -
Active set method - very robust but can be slow for Composite-size problems. Shadow prices are calculated for both LP and QP subproblems.
Keywords
DMCplus, External Targets, Steady-State Solution Option