Compound excitation DC machines and examples

[m-kormann]

Component models to implement compound excitation already existed and just had to be combined in the right way.

To allow modeling of a self-exciting DC generator, additionally I introduced saturation in the AirGapDC model.

It has to be discussed if the stray induction also needs a saturation model.

Summary by CodeRabbit

• New Features
  • Introduced simulation models for compound excited DC machines that integrate both electrical and thermal dynamics.
  • Added a quasi‐static variant for scenarios where fast electrical transients are not required.
  • Provided an example generator setup to demonstrate compound excitation in power generation.
  • Enhanced configuration options with a new parameter record for streamlined machine customization.

[CLAassistant]

All committers have signed the CLA.

[AHaumer]

I dislike the idea of introducing special effects (like saturation) into these models. If we do so, we should introduce saturation, deep bar effect, .... what else? in all machine models. To be honest, I don't have enough time neither to implement that nor to review that all. And remember, you'll have to provide at least one meaningful test case (that tries to detect all flaws ;-) We expect users that need such features to copy the corresponding models out of the MSL and adapt them to their needs.

[HansOlsson]

I dislike the idea of introducing special effects (like saturation) into these models. If we do so, we should introduce saturation, deep bar effect, .... what else? in all machine models. To be honest, I don't have enough time neither to implement that nor to review that all. And remember, you'll have to provide at least one meaningful test case (that tries to detect all flaws ;-) We expect users that need such features to copy the corresponding models out of the MSL and adapt them to their needs.

I can understand the dislike of special effects in such models; and instead of adding more special effects in an existing it would to me make more sense to demonstrate how such effects can be added in example-models (either by adding separate components in the example, or by having more advanced models with those effects (ideally built by composition of existing components, and possibly some new ones, since that would also indicate that the existing models can be re-used).

Some reasons are that:

• For understanding and education it helps to have a simple model without anything extra. (Tools can of course remove unnecessary equations when presenting it, but it is still a hurdle.)
• In some uses (like HILS) the extra equations may cause unnecessary problems.

[m-kormann]

Saturation was implemented to showcase the benefit of a compound-excited machine: Self-Excitation up to nominal voltage and keeping it constant under load. I was impressed myself that adding one simple effect such a behaviour can be modeled. But I agree with you. Once you start introducing a simple effect, where to stop going into details?

Basically saturation was just introduced by modifying the airgap model. So I will remove the saturation part from the MSL MR and adapt the example to work without self-excitation. Then a user could still implement saturation by replacing the airgap model.

[AHaumer]

@m-kormann to be honest, I understand your intention and the application. You see I've prepared the possibility of having a compound machine but I didn't have the time to implement it. DC machines have lost siginificance the past decades, but they're useful for education. So I'd suggest two possibilities:

1. Implement saturation in a 100% backwards compatible way and provide several additional example utilizing that, e.g. self-excitation of a parallel excited generator and self-excitation of a series excited machine for braking. Might be a lot of work and should be extended to quasi-static DC-machines.
2. Implement the compound machine (transient and quasi-static). Implement an example using that machine. If desired, implement saturated air-gap in Examples.Utilities.

[m-kormann]

@AHaumer Yes, DC machines have lost significance, but also in my opinion they are of high value for educational reasons. Using a compound DC machine as excitation machine I managed to model a synchronous generator keeping the output voltage nearly constant for different loads without the need of any controller.

So let's divide this topic into three parts and only implement the first one in this MR:

1. Implement the compound machine transient and quasi-static
2. Implement a saturated air-gap in Examples.Utilities
3. Implement saturation for all other DC machines for different applications

The quasi-static machine already was implemented and now I added it to the example.

[christiankral]

I made some attempts to model DC machiens with saturation some time ago, see Magnetic_DCMachines.

@m-kormann So one additional option still ist to create a separate public library with saturation models. On my opinion, there is no need to have saturation models in the MSL. Considering this option, you are very free to implement as many options as you like.

[m-kormann]

@christiankral This is a very good hint! I also had the thought to implement DC machines within Modelica.Magnetic.FundamentalWave, which I see you already have done. When I find time, I will implement the Compound Excited machine in your library.

Still I think the unsaturated Compound DC machine should go to MSL because half the path was already gone before.

[AHaumer]

@m-kormann please send me a personal mail. I'd like to exhange ideas privately: https://www.oth-regensburg.de/personen/detailansicht/anton-haa-haumer Additionally I have a small library with specical machine implementations (including saturaton) we could develop together with your ideas maybe for inclusion in MSL.

[coderabbitai[bot]]

Walkthrough

This update introduces a new Modelica model named DC_CompoundExcited in both the basic and quasi-static DC machine packages, complete with detailed parameters for electrical and thermal dynamics. A new simulation example, DCCE_Generator, is added to demonstrate its operation. Additionally, a new parameter record (DcCompoundExcitedData) is provided to encapsulate excitation characteristics. Package order files in the affected directories are updated to include these new components.

Changes

File(s)	Change Summary
Modelica/Electrical/Machines/BasicMachines/DCMachines/DC_CompoundExcited.mo	Added new model DC_CompoundExcited with electrical and thermal parameters, components, and annotations.
Modelica/Electrical/Machines/BasicMachines/QuasiStaticDCMachines/DC_CompoundExcited.mo	Added new quasi-static model DC_CompoundExcited (with quasiStatic=true and an extended icon).
Modelica/Electrical/Machines/Examples/DCMachines/DCCE_Generator.mo	Added new example model DCCE_Generator demonstrating power generation with compound excitation.
Modelica/Electrical/Machines/{BasicMachines/DCMachines, BasicMachines/QuasiStaticDCMachines, Examples/DCMachines}/package.order	Updated package order files to include new entries (DC_CompoundExcited and DCCE_Generator).
Modelica/Electrical/Machines/Utilities/ParameterRecords/DcCompoundExcitedData.mo	Added new record DcCompoundExcitedData extending parameter data for compound excitation.
Modelica/Electrical/Machines/Utilities/ParameterRecords/package.order	Updated package order to add the new DcCompoundExcitedData entry.

Sequence Diagram(s)

sequenceDiagram
    participant User as User
    participant Gen as DCCE_Generator
    participant DC as DC_CompoundExcited
    participant Data as DcCompoundExcitedData

    User->>Gen: Start simulation
    Gen->>DC: Instantiate compound excited model(s)
    DC->>Data: Request excitation parameters
    Data-->>DC: Supply parameter data
    DC->>Gen: Return simulation outputs

Poem

Hoppin' through the code with delight,
I found new models shining bright.
DC currents dance in compound flow,
Data records whisper soft and low.
With each new change, I skip and play—
A bunny’s cheer for a brighter day!
🐇✨

---

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