Solid-state transformers (SSTs) are employing compact high-power medium-voltage (MV) medium-frequency transformers (MFTs) and enable the power transfer between galvanically isolated DC systems. Considering a typical SST isolation stage, i.e., a 166 kW unregulated series-resonant DC-DC converter acting as a DC transformer (DCX) with equal input and output MV DC voltages of 7 kV (1:1-DCX), we derive component-level and system-level performance limits of aircooled realizations with either an air-core transformer (ACT) or with a magnetic-core transformer (MCT). We describe the design of two fully rated MFT prototypes in detail and provide a comprehensive experimental characterization to validate the derived performance limits, including also the dielectric losses and the analysis of stray magnetic fields. The realized ACT and MCT prototypes achieve measured efficiencies of 99.5 % and 99.7 % at gravimetric power densities of 16.5 kW/kg and 6.7 kW/kg, respectively. Considering 10 kV SiC MOSFETs, calculated system-level efficiencies of the ACT-based and MCTbased 1:1-DCX result in 99.0 % and 99.2 % at the nominal operating point, with similar part-load efficiency characteristics. The paper concludes with an application-oriented qualitative evaluation of the two concepts.
This article presents the study of the optimal design solutions for regeneration of marketplaces. It examines the design variants for the revitalisation of the marketplace, in particular, investment in their modernisation in order to find the most optimal model for transforming these public spaces to have a significant impact on the city’s development. The research is a comparative analysis of the implementation of regeneration design models on the marketplace within the Oliwa district of Gdansk (Poland).The data for the case study design models includes analysis based on various optimisation criteria, taking into account the urban and economic aspects of the city landscape when selecting a specific space revitalisation design model. The implementation of regeneration investment includes a number of complex processes that must be sustainable and so require rational social and spatial planning, as well as proper organisation in terms of cost and time.
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