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Purpose This paper aims to propose a new design for high-power compact solid-state transformers (SSTs) made with grain-oriented electrical steel (GOES) wound cores that benefit from the natural reduction of iron losses at high temperatures. Design/methodology/approach An experimental approach, coupled with numerical and analytical investigations, is widely used for proving the validity of the proposed concept. Findings With cores much hotter than coils, the new design of medium frequency transformers can be used for building compact SSTs that rated powers and common-mode insulation voltages much higher than existing ones with similar efficiencies. Research limitations/implications The thermal design must provide a large difference between core and coil temperatures in a reasonable volume. Practical implications The increasing number of intermittent renewable sources place electric grid stability at risk. Smart nodes, made of SSTs, improve the global grid stability because they are able to provide real-time control of energy fluxes at critical points. In railway applications, high-power SST cells can be distributed along the train providing a larger volume for passengers. Social implications The increasing part of electricity in a flexible grid requires performant and high-power SSTs made with components that have an environmental footprint as low as possible. Originality/value This paper proves that the design of high-power transformers with GOES wound cores much hotter than coils is possible. It proposes also a thermal equivalent circuit that helps the design.

All fields of activity using electric energy are more than ever challenged for efficiency and versatility of energy flow at reasonable costs. The emergence of electronic components with high voltage and current capabilities enables to cope with those challenges. The paper deals with assessments on Medium Frequency (MF) high-power Solid State Transformer (SST). A good technical-economic balance can be achieved by assembling suitable high power SST cells made with mature technologies for power electronics, magnetic cores and simple and reliable control strategies. In this framework, the study and design of a SST based on elementary cells involving a Grain Oriented Electrical Steel (GOES) core is addressed.

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