Bipolar output direct-coupled DC–DC converter applied to DC grids

Autor: Lingyu Guo, Gang Yao, Chengjun Huang, Lidan Zhou
Jazyk: angličtina
Rok vydání: 2019
Předmět:
Zdroj: The Journal of Engineering (2019)
Druh dokumentu: article
ISSN: 2051-3305
DOI: 10.1049/joe.2018.8808
Popis: The unipolar-input bipolar-output DC–DC converters with megawatt rating are the key equipment in the multi-terminal HVDC and DC grids, especially in the DC wind farm. This paper presents a novel direct-coupled transformerless DC–DC converter to interconnect unipolar DC system with bipolar DC transmission line based on cascaded sub-modules. The sub-modules can be achieved by active clamping (clamped diode), half bridge and full bridge. The proportional-integral control strategy is employed to balance the capacitors' voltages in several sub-modules and the energy between the upper and lower arms. Compared with other bipolar output DC–DC converters, the new direct-coupled DC–DC converter offers several merits: (1) The volume and the cost can be reduced due to the absence of the transformer and the large-scale sub-module capacitance; (2) There is no extra AC–DC conversion process, so it can achieve higher efficiency; (3) The IGBTs only turn on or off once in a period, which results in lower power loss; (4) High step-up ratio, redundancy, and fault tolerance can be achieved by changing the number of sub-modules. Finally, the simulation of the proposed DC–DC converter based on MATLAB/Simulink platform is given to verify the feasibility of the topology and the accuracy of the theoretical analysis.
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