Sample time in C-script ?

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1

Hi everybody,

I’m working on the MPPT control through c-script for a DC-DC converter (PLECS Standalone). The code is implemented but I don’t understand when i choose a sample time of 1/(switch frequency) (setup of the c-script-block) the model doesn’t work. I reduced the sample time at 0.05 and i have the good behaviour. As shown in the figure, the top signal represents the adapted voltage of the pv panel when a irradiation change occur and a sample time of 0.05.

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The next figure shows the voltage signal when i change the sample time of the c-script setup (1/switch frequency)

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Thank you for your help and response

Cheers

2

Hi there, are you able to post your model?

3

Hi, sure. In attached you have the model

BuckMPPT_V1.plecs (50.9 KB)

4

This is a control issue. Your perturb and observe will not work effectively at the switching frequency. Your determination of a value of 0.05 seconds makes sense, as that looks to be about the time-constant of your buck converter in response to a step-change in modulation index.

5

Hi, so it would be a control problem and not a setup problem of sample-time? I built a PWM signal with a frequency of 100kHz in order to have a bandwith of the minimum duty cycle calculated firstly

6

Hi, up because i don’t understand what happens with the sample time. Thank you