Over the recent years, smart grids have received great public attention. Many proposedfunctionalities rely on power electronics, which play a key role in the smart grid, togetherwith the communication network. However, “smartness” is not the driver that alone motivatesthe research towards distribution networks based on power electronics; the networkvulnerability to natural hazards has resulted in tightening requirements for the supply security,set both by electricity end-users and authorities. Because of the favorable pricedevelopment and advancements in the field, direct current (DC) distribution has becomean attractive alternative for distribution networks.In this doctoral dissertation, power electronic converters for a low-voltage DC (LVDC)distribution system are investigated. These include the rectifier located at the beginningof the LVDC network and the customer-end inverter (CEI) on the customer premises. Rectifiertopologies are introduced, and according to the LVDC system requirements, topologiesare chosen for the analysis. Similarly, suitable CEI topologies are addressed and selectedfor study. Application of power electronics into electricity distribution poses somenew challenges. Because the electricity end-user is supplied with the CEI, it is responsiblefor the end-user voltage quality, but it also has to be able to supply adequate current in alloperating conditions, including a short-circuit, to ensure the electrical safety. Supplyingshort-circuit current with power electronics requires additional measures, and therefore,the short-circuit behavior is described and methods to overcome the high-current supplyto the fault are proposed. Power electronic converters also produce common-mode (CM)and radio-frequency (RF) electromagnetic interferences (EMI), which are not present inAC distribution. Hence, their magnitudes are investigated.To enable comprehensive research on the LVDC distribution field, a research site wasbuilt into a public low-voltage distribution network. The implementation was a joint taskby the LVDC research team of Lappeenranta University of Technology and a power companySuur-Savon S¨ahk¨o Oy. Now, the measurements could be conducted in an actual environment. This is important especially for the EMI studies. The main results of the work concern the short-circuit operation of the CEI and the EMI issues. The applicability of the power electronic converters to electricity distribution is demonstrated, and suggestions for future research are proposed.
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