Study of Equilibrium Point Qualitative Behaviors in DC-DC Converters

The behavior of non-linear systems around the equilibrium points can be classified into stable or unstable node, stable or unstable focus, saddle point and limit cycle. In most cases, these behaviors can be established from the poles of the linear approximation around a given equilibrium point. In this paper the analysis of focus and node qualitative behaviors of DC-DC power electronics converters around a given equilibrium point is studied. Open-loop and closed-loop dynamics are considered. Three different laboratory prototypes of the converters are used, namely, an interleaved buck, an interleaved boost and a double buck with an inductor-capacitor input filter. These prototypes and analysis were used as an aid to study typical equilibrium point behaviors as an introduction to a non-linear system graduate course.