Isolated Bipolar Modular Multilevel DC-DC Converter with Self-balancing Capability for Interconnection of MVDC and LVDC Grids

Lai, Jinmu, Yin, Xin, Wang, Yaoqiang, Jiang, Lin ORCID: 0000-0001-6531-2791, Ullah, Zia and Yin, Xianggen (2023) Isolated Bipolar Modular Multilevel DC-DC Converter with Self-balancing Capability for Interconnection of MVDC and LVDC Grids CSEE JOURNAL OF POWER AND ENERGY SYSTEMS, 9 (1). pp. 365-379. ISSN 2096-0042, 2096-0042

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Abstract

Bipolar medium-voltage DC (MVDC) and low-voltage DC (LVDC) grids have the advantages of flexible integration of distributed renewable-energy generation and reliable power supply. In order to achieve voltage conversion, power transfer, and electrical isolation for bipolar MVDC and LVDC grids, a high-power DC-DC converter is essential. Therefore, this paper proposes an isolated bipolar modular multilevel DC-DC converter (BiMMDC) with power self-balancing capability for interconnection of MVDC and LVDC grids. The proposed BiMMDC consists of two series connected MMCs in the MV stage to configure a bipolar MVDC interface, and interleaved converters combined with a dual-transformer are designed in the LV stage to configure the bipolar LVDC interface and to provide a self-balancing capability. Equivalent circuits of two series-connected MMCs and a dual-transformer with interleaved converters are derived. After that, operation principles of the proposed BiMMDC are introduced, considering balanced/ unbalanced power transfer of bipolar LVDC grid and monopolar short-circuit or open-circuit faults at MVDC grid. The control scheme is also presented for the proposed BiMMDC under different operating conditions. Finally, a Matlab simulation and controller hardware-in-the-loop (CHIL) evaluation results are provided to validate the feasibility and effectiveness of the proposed typology and its operating performance.

Item Type:	Article
Uncontrolled Keywords:	Circuit faults, Voltage, DC-DC power converters, Power transformer insulation, Equivalent circuits, Capacitors, Inductors, Bipolar, DC-DC converter, equivalent circuit, modular, monopolar operation, multilevel, self-balancing
Divisions:	Faculty of Science & Engineering > School of Electrical Engineering, Electronics and Computer Science
Depositing User:	Symplectic Admin
Date Deposited:	07 Mar 2023 16:03
Last Modified:	16 Jun 2026 10:30
DOI:	10.17775/CSEEJPES.2022.05460
Open Access URL:	https://ieeexplore.ieee.org/document/9979744
Related Websites:	Author Publisher
URI:	https://livrepository.liverpool.ac.uk/id/eprint/3168821
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