Bifurcation-Based Dynamical Stability and Coupling Analysis of Dual-Input Buck-Boost DC-DC Converters

Different from single-input single-output (SISO) converters, strong nonlinear coupling effect between input ports is one of the most salient features in multi-input converters (MICs), which leads to at least three-piecewise ripple of inductor current. This paper deals with the analysis of bifurcation-based dynamical stabilities and nonlinear coupling effects in the dual-input Buck-Boost DC-DC converter. Firstly, a sampling-based averaged continuous model is proposed to describe the coupling characteristics of the dual-input DC-DC converters with three-piecewise current ripple. Based on the proposed model, the inherent mechanism of low-frequency oscillation is revealed in terms of the movement of the eigenvalue loci. It shows that Hopf bifurcation takes the responsibility for the low-frequency oscillation. Moreover, multiparameters stability boundaries are identified to establish the nonlinear mapping relations between parameter space and state space. Particularly, Gershgorin band analysis is used to give a qualitative analysis in order to evaluate the coupling effects between different state variables of the system. In addition, Gershgorin band sensitivity is proposed to reveal the influence of parameters on the coupling effects of the system. Finally, the correctness of these theoretical analyses is verified by PSpice circuit experiments. These results are beneficial to the practical optimization design as well as the understanding of coupling effect of MICs.