One important tip is to relay on the physical model of the system and or system components to assess the feasible initial values for the parameters. Always the physical model and the experimental results will lead you to solution conversions.

The other way is to analyse the performance of the numerical solution and detect the major factor causing the divergence.

Best wishes

Abdelhalim abdelnaby Zekry I am using Dymola currently, but with initialization divergence, there is no numerical solution information. Do you have any suggestions with this situation?

Yiwei,

I think the main cause of divergence is the division by very small quantities that may lead to large numbers outside the dynamic range of the processor.

So, you have to return to your mathematical model of your system.

The other cause is the presence of growing functions in the solution which means you system can contain poles in the write hand side of the complex frequency domain, the S-domain.

In order to solve the convergence problem you must study the nature of your equations.

Best wishes

Abdelhalim abdelnaby Zekry Thank you for your advices. I managed to find the "bad" start value for the iteration variable, hope in the future the solver used for modelica tools could be more strong so that I wouldn't need to worry about divergence.

According to the comparison between ThermoSysPro(Open source library from EDF https://github.com/alex19941215/ThermoSysPro ) and ThermalPower(Commercial library from Modelon https://www.modelon.com/library/thermal-power-library ), there should be some inspiration for people faced with the same situation.

Here is the code form ThermoSysPro library:

Connectors.FluidInlet Ce

Connectors.FluidOutlet Cs

Here is a type code from Thermal Power library:

Interfaces.FlowPort feed(

h_outflow(start=hstartin))

Interfaces.FlowPort drain(

p(start=pstart),

h_outflow(start=hstartout))

From the code, we can see that in the Thermal Power library each connector's attribute is assigned values according to the parameters, but in the ThermoSysPro library, the connector is using default values, probably zero. So that's why the Thermal Power library has better performance in the term of initialization convergence