Buck-Boost Converter

Introduction

This example contains a transient model of a DC-DC buck-boost converter. In this notebook the discontinuous conduction mode of the converter will be studied.

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Wolfram SystemModeler; a free trial download is available at www.wolfram.com/system-modeler

The model that came in the same bundle as this notebook

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Initialize

Define the model name:

mmodel="EducationExamples.ElectricalEngineering.BuckBoostConverter";

Detect Discontinuous Conduction Mode

Discontinuous conduction mode (DCM) is when the inductor current goes to zero. For loads below this level, inductor current cannot reverse through the diode. There are a number of problems that have to be addressed when in DCM:

Increased device stress, and higher ratings of the passive components are needed.

Noise and EMI.

You can identify DCM with SystemModeler and the Wolfram Language. Simulate the model:

sim=Quiet[SystemModelSimulate[mmodel,{0,0.05},<|"ParameterValues"->{"r1"->500}|>]];

Pick out a slice of the simulation data:

dataMin=({#,sim["inductor.i"][#]}&@Range[0.024,0.02415,0.0000005])\[Transpose];

Find the times when inductor current is zero or very close to zero:

meshvals=Map[{First[#],Last[#]}&,Quiet[FindClusters[Rest@Select[dataMin,#[[2]]<=0.0001&][[All,1]]]]]

Plot the inductor current and highlight the periods where the inductor current is zero:

Plot[{Evaluate[First[sim[{"inductor.i"},t]]]},{t,0.024,0.02415},Mesh->{Flatten[meshvals,1]},MeshShading->{Automatic,Red},AxesLabel->{"Time [s]","Current [A]"},PlotLabel->"Inductor current"]

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