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The increasing interest in Hybrid Electric Vehicles led to the study of new powertrain structures. In particular, it was demonstrated in the technical literature how series architecture can be more efficient, compared to parallel one, if supercapacitors are used as storage system. Since supercapacitors are characterized by high efficiency and high power density, but have low specific energy, storage sizing is a critical point with this technology. In this study, a detailed analysis on the effect of supercapacitor storage sizing on series architecture was carried out. In particular, in series architecture, supercapacitor storage sizing influences both engine number of starts and the energy that can be stored during regenerative braking. The first aspect affects the comfort, whereas the second aspect directly influences powertrain efficiency. Vehicle model and Energy Management System were studied and simulations were carried out for different storage energy, in order to define the optimal sizing.

High-power converters with a medium frequency inductive coupling, commonly referred as Power Electronic Transformers, Medium Frequency Topologies, Solid-State Transformers (SST), or other similar acronyms, have been certainly one of the most important innovations expectations - for many years - in the field of electrical equipment of the railway rolling stock. The main purpose of these topologies is to replace the usual line-frequency on-board transformer on the AC powered rolling stock (25 kV - 50 Hz and 15 kV - 16 2/3 Hz), bulky, heavy and characterized by rather poor efficiency

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