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Need help modeling a Buck/Boost Converter in Simulink/Simscape

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Gowthum Sekar
Gowthum Sekar on 8 Jul 2014
Answered: Mahmoud Saleh on 4 Aug 2017
Hi all:
I'm working on modeling a Buck/Boost Converter that can take an input voltage signal from 0.5 v to 24 v and can output at a voltage of 12 v. The gist of the problem is that its not happening, the output is far too low.
Some notes on the design:
1) The current is routed through the converter via two MOSFET transistor blocks named Tr1 and Tr2. They are controlled such that. a) During boost mode, Tr1 is kept in the ON state via a constant voltage source at 12 v and Tr2 is switched via a PWM source block. b) During buck mode, Tr1 is switched via the PWM block and Tr2 is kept in the OFF state.
2) The inductor and capacitor are both variable blocks and are modulated via a control system that uses equations I developed. a) They yield results based on the difference between the output and input voltages and should correspond to results obtained here. http://www.daycounter.com/LabBook/BuckConverter/Buck-Converter-Equations.phtml
b) The switching frequency was set at 1 kHz, the minimum output current was set at 0.5 A, the output current at 1 A and voltage ripple at 10%
The control system was done in Simulink and the converter itself was done in Simscape. I've attached a few screenshots since it seems like I can't attach the file itself.
Thanks in advance! :D
PS: The software I used was matlab 2012b. I've made some modifications using matlab 2012a

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Answers (1)

Mahmoud Saleh
Mahmoud Saleh on 4 Aug 2017
Check out those two models for boost and bidirectional dc/dc converter. An explanation can be found in the Simulink model. Those model were meant for Microgrid application (higher voltage and current), but the values can be easily adjust to work with lower values:
https://www.mathworks.com/matlabcentral/fileexchange/63949-voltage-control-dc-dc-boost-converter
https://www.mathworks.com/matlabcentral/fileexchange/63791-voltage-control-dc-dc-bidirectional-converter

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