[TRNSYS-users] Message 441
Diego A. Arias
daarias at wisc.edu
Wed Jul 26 08:16:44 PDT 2006
Dear Constanze,
I would not recommend reducing the convergence criteria as much as you
are doing. This would make the results meaningless.
Remember that TRNSYS' solver is a numerical procedure, and you should
always keep that in mind. Think of your simulation as a system of
equations. The default solver uses successive substitution in order to
solve the system of equations. All iterative numerical methods are
based on a guess or initial values, that are used as starting point for
the iterations. If your system of equations is very complex, you have
to give good guess values. Sometimes, this feels like you have to give
the answer so the program gives you the back the same answer.
My suggestion to debug the system is that you start by making sure that
you do not get that warning message during one time step. If you get
this message, it means that you should change your initial values. In
the Studio, when you double click on a component, the initial values are
those that appear in the tab 'input'.
Another suggestion is to try to find the information flow that is
causing problems: try deleting the connection between some components,
and see if your simulation converges. This will show you the variable
that is causing the convergence problem.
If you still keep having problems, please feel free to send me the
project files and I will try to see what may be the problem.
Best regards,
Diego
Constanze.Bongs at csiro.au wrote:
> Hi,
>
> During simulation the following warning occurred:
> Message 441: The inputs to the listed units have not converged at this
> timestep. The values of the last iteration will be used to proceed.
>
> As I get this message more than thirty times Trnsys sends an error
> message and stops the simulation.
>
> I already set the tolerance convergence to 0.5 (from 0.001) and
> tolerance integration to 0.01 (from 0.001).
> Can you explain to me what is happening and how I can fix it? Does this
> mean that the system is too complex to be solved and are the simulation
> results still useful? Which maximum values for tolerance convergence and
> tolerance integration still manage to give me reasonable results?
>
> Cheers,
>
> Constanze
>
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> TRNSYS-users at engr.wisc.edu
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>
--
Diego A. Arias
TRNSYS Coordinator
Solar Energy Laboratory
University of Wisconsin - Madison
1500 Engineering Drive
Madison, WI 53706
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