New hybrid iron-ferrite-core coupling reactors upgrade effectiveness of H-bridge-based power conversion structures

Within the field of multilevel power conversion structures, the paper deals with analysis and improvements of the H-Bridge-based power conversion structure. This is considered as a novel basic cell generally applicable to voltage-supplied power converters. Its fundamental properties as a three-level PWM conversion block are analysed for better definition of the output coupling reactor design requirements. As shown according to reported analysis of H-Bridge cell operation, two flux components are inherent with the function of the coupling reactor. A more clear comparative evaluation of bookish and other prototype solutions is achieved. On the same basis, a new family of coupling inductor structures is comparatively defined and presented for the first time. The new family is characterized by hybrid iron-ferrite cores, as far as its effectiveness is related to the feasibility of good separation between the two different flux components. Drafts of different hybrid core implementations are reported and related to power rating, namely U-C and E-C core families. A prototype design of a power U-C hybrid core is presented, according to 30 kW automotive traction application. Proper experimental test procedures are reported to model the different secondary effects, as for iron and skin effect losses.