Thermal behavior of grain-oriented electrical steel wound core solid-state transformer

Abstract

PurposeThis 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/approachAn experimental approach, coupled with numerical and analytical investigations, is widely used for proving the validity of the proposed concept.FindingsWith 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/implicationsThe thermal design must provide a large difference between core and coil temperatures in a reasonable volume.Practical implicationsThe 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 implicationsThe 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/valueThis 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.