Saddle-Node Bifurcation Associated with Parasitic Inductor Resistance in Boost Converters
For power electronics engineers designing boost converters, this work reveals a previously overlooked bifurcation mechanism that can cause instability, emphasizing the need to model parasitic resistance in compensator design.
This paper identifies saddle-node bifurcation in boost converters when parasitic inductor resistance is modeled, deriving closed-form critical conditions. It shows that such bifurcation can cause multiple steady-state solutions and voltage jumps, which are absent when parasitic resistance is ignored, potentially misleading design.
Saddle-node bifurcation occurs in a boost converter when parasitic inductor resistance is modeled. Closed-form critical conditions of the bifurcation are derived. If the parasitic inductor resistance is modeled, the saddle-node bifurcation occurs in the voltage mode control or in the current mode control with the voltage loop closed, but not in the current mode control with the voltage loop open. If the parasitic inductor resistance is not modeled, the saddle-node bifurcation does not occur, and one may be misled by the wrong dynamics and the wrong steady-state solutions. The saddle-node bifurcation still exists even in a boost converter with a popular type-III compensator. When the saddle-node bifurcation occurs, multiple steady-state solutions may coexist. The converter may operate with a voltage jump from one solution to another. Care should be taken in the compensator design to ensure that only the desired solution is stabilized. In industry practice, the solution with a higher duty cycle (and thus the saddle-node bifurcation) may be prevented by placing a limitation on the maximum duty cycle.