The Journal of Engineering (Jan 2019)
Design and control of a SiC-based three-stage AC to DC power electronic transformer for electric traction applications
Abstract
By operating at much higher frequencies, power electronic transformers (PETs) offer many advantageous features consisting of high power density, high efficiency and diverse functionalities. But the trade-off between the operating frequency and the conversion efficiency limits the further development of PETs. Nevertheless, with the advancements on SiC-MOSFET devices, this limitation can be overcome due to the higher blocking voltage utilisation factor and lower on-state losses of SiC devices. The potential applications of the proposed SiC-based PET are railway traction for electric multiple units (EMUs), interfacing electric vehicles, marine propulsion, etc. This paper focuses on a SiC-based three-stage AC to DC PET, which employs an input series and output parallel (ISOP) configuration. By synthetically comparing some typical topologies of PETs, their merits and demerits are summarised. By minutely analysing requirements and rigorously calculating, the design of the high power medium-frequency transformer (MFT) is presented. By operating simulations of topological structures of the proposed PET on the basis of MATLAB/Simulink, control strategies including phase-shift control and voltage balancing control are described. Simulations with prototype model are provided to demonstrate the operation of the PET.
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