Analysis of AC link topologies in non-isolated DC/DC triple active bridge converter for current stress minimization

This paper presents analysis of the non-isolated DC/DC triple active bridge (TAB) converter under various purely inductor-based AC link topologies. The objective of the analysis is to find the topology that incorporates the least value of the AC link inductors which leads to reduced converter footprint in addition to minimum internal current stresses. Modelling of the TAB under each of the different topologies is presented in per unit expressions of power transfer and reactive power assuming fundamental harmonic analysis. The power expressions are used to calculate the inductor values necessary to achieve same rated power transfer of Dual Active Bridge (DAB) converter for the sake of standardizing comparison. On this basis, the topology requiring the least value of interface inductors, hence lowest footprint, is identified. Furthermore, based on phase shift control, particle swarm optimization (PSO) is used to calculate optimal phase shift ratios in each of the proposed topologies to minimize reactive power loss (hence current stress). The topology with minimum stresses is therefore identified and the results are substantiated using a Matlab-Simulink model to verify the theoretical analysis.