How to simulate in function of duty cycle instead of time?

Dear colleagues,

I'm doing the bachelor thesis about using dc-dc converters with PV Panels. See 1st photo

When I run the model it run in function of time, but I would like to do a simulation with the duty cycle in the Scopes. I mean, to show the output values when the converter works with different duty cycle (I don't care about time).

I don't know how to do it and I would be very grateful if you could give me a clue or a help with that.

Thank you in advance.

Answer 1

[Joel Van Sickel]

Hello Pedro,

To do this live, you can use the x/y graph: https://www.mathworks.com/help/simulink/ug/plot-circle-with-xy-graph.html

It might be a bit noisy, if you want to post process the data to remove noise, please see below.

To do this with clean data, you'll only want the steady state solution. I would model the system in time, and step it through a few discrete duty cycles, for instance, 0.1, 0.2, 0.3, 0.4, 0.5, etc. Then you can take the steady state operating point for each duty cycle and plot that vs duty cycle. This will require creating a matlab script to post process the data and plot it after the simulation has run.

Regards,

Joel

[Pedro José Servián García]

Thank you Joel, my only additional question is if you know if there is any tool to take the steady state of the reponse. Thanks!!!!

[Joel Van Sickel]

Hello Pedro, unfortunately, I don't know a tool that will automatically do it. What I would do is use this block: https://www.mathworks.com/help/simulink/slref/toworkspace.html

then, at fixed time intervals, change your duty cycle. You can then grab the data from the moment before you change your duty cycle and that will be your steady state result if the system has been given enough time to hit steady state.

[Pedro José Servián García]

Hello Joel, finally I used it to fix my problem, thank you very much!!!!! I have another query about an error in the PV Array, I don't know if you could help me. It's on another question thread