A Modular Multilevel Converter with a Zigzag Transformer for Bipolar MVDC Distribution Systems

Cui, Shenghui; Lee, Joon‐Hee; Hu, Jingxin; Doncker, Rik W. De; Sul, Seung-Ki

doi:10.1109/tpel.2018.2855082

Cited by 45 publications

(13 citation statements)

References 12 publications

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“…This multiport autotransformer only processes partial power and thus an improvement in conversion efficiency is obtained. In [13], [20], [21], MMC-based dc-dc converters have been adapted for ac grid connectivity by multitasking the transformers to carry both dc and ac currents. Some multi-port MMCs are examined and compared in [5], but the comparison is limited to a couple of basic design scenarios and so few general conclusions are drawn.…”

Section: P S Gmentioning

confidence: 99%

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Comparative Assessment of Multi-Port MMCs for High-Power Applications

Kish

2022

IEEE Access

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Multi-port converters can interconnect different dc and ac systems while reducing semiconductor requirements and losses by eliminating redundant power conversion stages. Modular multilevel converter (MMC)-based multiport systems are well suited for application in mixed ac-dc grids containing high-voltage dc (HVDC) and medium-voltage dc (MVDC) systems. This paper conducts a detailed comparative assessment of multi-port dc-dc-ac MMCs for high power applications. Four representative topologies are chosen for study due to their contrasting internal power processing characteristics. Three different network scenarios are investigated that include HVDC and MVDC applications, covering several different power flow cases. The multi-port MMCs are compared in terms of losses, semiconductor effort, internal energy storage and magnetics requirements. The results are extensively discussed and general conclusions are summarized. INDEX TERMS Ac and dc grids, dc-dc modular multilevel converter, multi-port converter.NOMENCLATURE

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Section: P S Gmentioning

confidence: 99%

“…Multi-port MMC topologies, e.g. [17], [21]- [23] are not compared here as they share strong structural similarly to the four representative topologies. Each multi-port MMC interfaces two dc systems, V dc,p and V dc,s , with an ac system.…”

Section: Multiport Mmcs Under Studymentioning

confidence: 99%

Comparative Assessment of Multi-Port MMCs for High-Power Applications

Kish

2022

IEEE Access

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“…As a result of the high penetration of RESs with different voltage levels, these converters and DC transmission lines get many attention [51]. The construction of MVDC grids and effective power transfer between various schemes including monopolar and bipolar MVDC grids need MV DC-DC converters for interfacing purposes [10], [87], [88]. Also, the interaction between HVDC transmission lines and MVDC distribution grids can be achieved by a converter with the characteristics of high voltage stepping-up ratio and high power ratings with FTC [5].…”

Section: A DC Grids Interconnectionmentioning

confidence: 99%

“…Choosing MVDC converters is subjected to some matters that should be taken into account to ensure adequate power conversion. Such converters are required to provide high efficiency and high step-up ratio [10]. The variation in both input and output voltages should be in a specific range, and the power rate starts from tens to hundreds of megawatts.…”

Section: Introductionmentioning

confidence: 99%

Isolated and Nonisolated DC-to-DC Converters for Medium-Voltage DC Networks: A Review

Alhurayyis¹,

Elkhateb²,

Morrow³

2021

IEEE J. Emerg. Sel. Topics Power Electron.

115

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MVDC technology is a promising solution to avoid installation of new AC networks. MVDC can provide optimum integration of large-scale renewable energy sources, the interconnection of different voltage levels of DC and AC grids with the ancillary services. The development in MVDC depends significantly on the DC-DC converters. Such converters support the modern trends of utilising medium-frequency transformers in power networks. Research on isolated converters technology is in its infancy and limited by the conversion ratio and component ratings. Besides, there is no standards exist covering specific aspects of isolated converter product. Thus, a review of such converters is needed. This work presents, for the first time, a review of the DC-DC power converter families in MVDC grids including the leading families which are isolated and nonisolated converters, as well as other subfamilies comparing the specifications and characteristics. Also, the applications of these converters are provided by focusing on the essential requirements for each application. Index Terms-MVDC grids, DC-DC power converters, dual active bridge (DAB), multilevel converter. TABLE I RECOMMENDED CLASSES FOR MVDC VOLTAGE MVDC Class (kV) Nominal Rated Voltage (kV) Maximum Rated Voltage (kV)

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“…Nevertheless, the isolation feature is important for the operation, thus a transformer must be incorporated into the structure. One possibility is to create a mix of modular multilevel converters and low-frequency transformers [8], [9]. Another alternative is to operate the transformer with a frequency higher than the ac power line.…”

Section: Introductionmentioning

confidence: 99%

A Unidirectional Insulated AC–DC Converter Based on the Hexverter and Multipulse-Rectifier

Lambert

Costabeber

Wheeler

et al. 2020

IEEE Trans. Power Electron.

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This paper proposes an insulated two-stage ac-dc converter to be applied in unidirectional power flow systems. The two-stage structure is the combination of a Hexverter and a series-type 12 pulse rectifier. The key features of the proposed structure are inherited from the modular multilevel converter concept such as modularity, scalability, and expandability. Besides the topology, this article presents a complete control strategy based on the output (dc) voltage regulation and Hexverter's stored energy. In particular, an unusual method to regulate the Hexverter's branch energy unbalances is proposed. All currents in the Hexverter are controlled which increases the robustness for operation in harsh environments such as subsea systems. Mathematical analysis of the control loops is carried out to develop the necessary control-oriented models for each control loop. The converter and the control strategy are verified through experiments in a 24 cells Hexverter and a current-fed series-type 12-pulse rectifier.

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A Modular Multilevel Converter with a Zigzag Transformer for Bipolar MVDC Distribution Systems

Cited by 45 publications

References 12 publications

Comparative Assessment of Multi-Port MMCs for High-Power Applications

Comparative Assessment of Multi-Port MMCs for High-Power Applications

Isolated and Nonisolated DC-to-DC Converters for Medium-Voltage DC Networks: A Review

A Unidirectional Insulated AC–DC Converter Based on the Hexverter and Multipulse-Rectifier

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