A cascaded converter interfacing long distance HVDC and back-to-back HVDC systems

Xiang, Wang and Yang, Ruizhang and Lin, Chang and Zhou, Jiapei and Wen, Jinyu and Lin, Weixing (2019) A cascaded converter interfacing long distance HVDC and back-to-back HVDC systems. IEEE Journal of Emerging and Selected Topics in Power Electronics. ISSN 2168-6777 (https://doi.org/10.1109/JESTPE.2019.2913915)

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This paper proposes a cascaded converter dedicated to long-distance HVDC infeed and asynchronous back-to-back interconnection of receiving grids. The cascaded converter is consisted of MMCs in series and parallel connection, meeting the high DC voltage and power demand of HVDC system. It realizes hierarchical feeding and asynchronous interconnection of receiving grids, optimizing the multi-infeed short circuit ratio and improving the flexibility of the receiving grids. The topology and operating characteristics of the cascaded converter are introduced in detail. The multi-infeed short-circuits ratio (MISCR) and the maximum power infeed of the cascaded converter based HVDC systems are analyzed. Various feasible operating modes with online switching strategies of the cascaded converter are studied to improve the operational flexibility of the system. The simulation results verify the effectiveness of the control strategy of the HVDC system embedding the cascaded converter. The DC faults clearing strategy and operating modes switching strategies are also validated.