Dear
In PLECS, I’m simulating an AFE converter for which I also created a thermal model.
To do this, I imported the thermal models of the diodes and IGBTs from the converter into the thermal library so they can be used within the components.
However, when I enable the thermal model of the IGBTs, my control system no longer works correctly. I get a DC voltage of 500 VDC instead of 700 VDC.
When I disable the thermal model of the IGBTs, the system does regulate correctly to 700 V DC.
I don’t understand why this happens and I have no idea how to fix it.
Therefore, I’m including the PLECS file and the thermal models in this post.
I’m attaching the PLECS file and thermal models in two separate posts due to attachment limits (other post title: AFE Converter Control Fails When IGBT Thermal Model Is Enabled in PLECS (1))
Thanks for the help in advance!!!
Kind regards
Milan
AFE_with_thermal_IGBTs.plecs (556.3 KB)
AFE_without_thermal_IGBTs.plecs (549.8 KB)
Hello MilanVdW, in PLECS the thermal domain does not effect the electrical domain. This is still true in your simulations.
However, your control logic includes temperature dependent drive enable/disable which will impact your converter operation. In other words, your controller is not being driven and only performing passive rectification and thus the bus regulation operation is different between the two simulations.
If you remove the temperature dependent drive logic then your converter operations will be identical.
Hope this helps!
Dear Ahmed,
First, I want to thank you for your help.
The IGBTs will indeed switch off when their temperature exceeds 149°C (subsystem AFE). However, this condition applies specifically in the case of a short circuit in the AFE converter. In steady-state operation, where the load is 132.94 A, the IGBT’s do not overheat, and the converter maintains a stable 500 VDC.
This leads me to wonder: is there another component or mechanism responsible for this behavior?
To summarize my question: where exactly is the temperature-dependent drive located? If it is the part mentioned in the scope, I don’t believe it is the source of the issue—because in my simulation, the IGBT’s do not reach critical temperatures.
Kind regards,
Milan
Hi MilanVdW,
From the simulation that I was running based on the files you provided I see the junction temperature reach ~0.1 MEGA degrees celsius!!!
The >149C logic that you’ve put into your simulation is what I was referring to when I mentioned temperature dependent drive - sorry should have been more verbose on what I meant. Here is a snapshot of what I am seeing from your simulation:
Could you confirm if you are seeing the same thing on your side?
I would think that the issue is coming from the thermal models and while you debug that section it would be best to disable the temperature dependent drive (thankfully in simulation your IGBT won’t catch on fire!!)
Hope this helps,
Munadir
