Bifurcation and stability analysis of a Dual-Active-Bridge dc-dc converter working under non-linear control

The Dual-Active-Bridge dc-dc converter is increasingly used in different fields of power electronics. This converter has different advantages compared to other topologies but can run into its operating range in areas of instability that limit its application. For this reason, the paper develops an accurate discrete large-signal sampled-data model of the controlled converter, then it carries out a stability and bifurcation analysis of the system to determine guidelines to increase the stability region of the controlled system. The control strategy is a discrete non-linear method based on the linearization of Jacobian matrixes. Then the tuning of regulator is a dynamic pole placement implemented using root locus analysis; the assigned poles have been chosen minimizing the 2norm of eigenvalues. This tuning process results in a combination of the pole placement strategy and of the gain scheduling approach, that means both robust and adaptative. Such analysis has been verified by MATLAB simulations. The numerical results show the strong dependence of the stability of the controlled system on the resistance of the output filter capacitor and on the parameters of controller.