Global Dynamical Analysis of a Boost Converter with a Constant Power Load and Actively Damped by a Series Loss-Free Resistor

Two-stage cascaded DC–DC converters appear in many power electronics engineering applications. In this cascaded scheme, the first stage is called the source or upstream converter while the second one is called the load or downstream converter. If the downstream converter is controlled to maintain a tightly regulated output voltage on the load, it behaves as a constant power load (CPL) for the source converter. The overall dynamics of this arrangement tends to be unstable, so it can be stabilized by means of a suitable feedback, or instead in open loop operation, by using an additional resistor, which can be a loss free resistor (LFR), thus avoiding efficiency losses. This work deals with the dynamical analysis of an open-loop DC—DC boost converter with a stabilizing resistor in series with the inductor and a constant power load by means of an averaged model. Fold and Hopf bifurcations explain the existence and stability conditions of the two possible equilibrium points. Moreover, an appropriate design requires not only that the equilibrium point must be stable but also that its basin of attraction must be large enough to include normal initial conditions. Then, we make an extended analysis taking into account the global dynamics of the system, mainly related to the saddle stable manifold or to an unstable large limit cycle, whenever it exists.