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Simulation speed reduced when using Simscape PWM Generator

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Sreeraj A
Sreeraj A on 9 Sep 2020
Commented: Joel Van Sickel on 16 Sep 2020
Hello !
Model having LLC resonant converter plant when integrated with a pulse generator using simscape PWM Generator performing extremly slow. !! Without the PWM Generator block model finish the execution quickly. Also, I can observe that when changing the frequency to normal hz range, simulation is speeding up ! but unfortunatly the model need to run at converter resonant frequency (250Khz) any help would be much appreciated.
Attached sreenshot of the model.
Thanks
Sreeraj Arole

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Answers (1)

Joel Van Sickel
Joel Van Sickel on 9 Sep 2020
Hello Sreeraj,
the speed of your simulation is inversely proportional to the frequency content in it. For instance, if I have a simulation with switching frequency of 1 khz, and resonant frequency of 10 khz, the simulation with resonant frequency of 10 khz, will be 10 times slower than the simulaiton with resonant frequency of 1 khz. It is understandable that you would see a significant slow down when adding your PWM at this has drastically decreased the minimum time step required to simulate it correctly. In order to speed up the simulation, please make sure to use piecwise linear switching devices. If you use a fixed step simulaiton, try using a fixed step 100 times smaller than your switching frequency, and if you are using a variable step solver, please try using odeN with ode14x, and set your step time to 5 to 10 times smaller than your switching frequency.
Here is a starting point for using mathworks tools for power electronics: https://www.mathworks.com/solutions/power-electronics-control/power-electronics-simulation.html
Regards,
Joel

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Joel Van Sickel
Joel Van Sickel on 10 Sep 2020
Hello Sreeraj,
I can't give you a specific number for that as it's highly dependent on your computer and complexity of the circuitry and other models.
The error you are getting is because something in your model is not converging. There are multiple causes for this. It could be how the model is set up, or it could be the solver settings. Your previous screen shot showed open loop control, in which case, I would guess that it is solver settings, but I usually see this error when there is a closed loop or ideal switches are being used. Are you able to share your model? If you cannot share your model on this forum, please contact technical support for further help.
Regards,
Joel
Sreeraj A
Sreeraj A on 12 Sep 2020
Hello Joel,
Thank for the suport.
I am currently runnin the model in open Loop. Currently building Open Loop CLLC resonant converter and using Ideal switches in my model. Would that be causing the issue ? attached model screenshot.
Joel Van Sickel
Joel Van Sickel on 16 Sep 2020
Hello Sreeraj,
unfortunately, the ideal switches usually cause problems because the diode isn't added in parallel. You have added a diode so it is less likely this is the issue. However, you could still try using a mosfet or IGBT block to see if that improved performance.
Regards,
Joel

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