—The efficient supply of electric power relies strongly on the selection of suitable voltage levels for different sections of the energy distribution system. When higher levels of power are required, a medium-voltage level in the tens of kilovolts range is typically selected. In accordance to current trends in energy conversion, the supply of power must fulfil several functionality requirements among which high power-quality and access to a low-voltage DC interface can be highlighted. Moreover, low energy losses, high power-density, low failure rate and low total cost of ownership remain as major research challenges. Solid-state-transformers (SSTs) comply with these functionality requirements as well as with the demanded high performance levels while directly connecting to medium-voltage. This paper reviews the implementation of SST technology for transportation and Smart-Grid applications. The envisioned architectures for locomotive systems, remotely-operated-vehicles and large scale ships, which benefit from the compactness and high performance of SST are shown. In addition, the possible arrangement of micro-grid systems comprising SST concepts for integration of renewable energy and implementation of DC- microgrids is detailed. The different SST concepts proposed for these applications can be grouped into distinctive categories, leading to a comprehensive classification of, first, general isolated AC-AC conversion systems and later to a specific classification of SST concepts based on the different levels of modularity. Finally, a detailed review of the numerous previously reported and functional SST concepts is presented and a comparison to systems employing low-frequency transformers is given.
This paper presents a concept of high frequency link for offshore wind applications based on a reduced matrix converter oriented to reduce the size and volume of the elements in the nacelle. A modular approach aimed at increasing reliability of the conversion system, which can be used in series or parallel connection of the off shore grid is also presented. Features of the proposed conversion concept related to ride through capability, protection strategies and parameters of the high frequency transformer are investigated. A modified space vector modulation is presented which reduces the losses in the conversion system.
