The Resonant Modular Multilevel DC Converters for High Step-ratio and Low Step-ratio Interconnection in MVDC Distribution Network

Xiang, Xin; Zhang, Xiaotian; Zhu, Yue; Chaffey, Geraint; Gu, Yunjie; Green, Tim

doi:10.1109/iecon.2019.8926939

Cited by 5 publications

(2 citation statements)

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“…Thus, the same resonant frequencies and circuit parameters for the SM stack are preserved. This scheme would have clear advantages in the circuit design over the resonant mechanism which occurs outside the SM stack [42]. In that evolution steps, the resonant frequencies are inevitably changed during reconfiguration from high step-ratio RMMC to low stepratio RMMC and redesign of the parameters of resonant SM stack is needed for each configuration.…”

Section: Low Step-ratio Rmmcmentioning

confidence: 99%

“…In addition to the MMC-based circuits mentioned so far, the transformer-coupled resonant modular multilevel dc-dc converter (RMMC) [37]- [39] was proposed for connection between MVDC and LVDC distribution networks where a high step-ratio conversion is needed. It inherits important advantages of both the classic LLC resonant circuit and the MMC structure, and it becomes a promising solution for MVDC distribution systems [40]- [42]. The purpose of this paper is to present how this RMMC can be reconfigured to bring those same benefits to a low-step ratio converter for interfacing two MVDC networks of similar but not identical voltages.…”

Section: Introductionmentioning

confidence: 99%

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Resonant Modular Multilevel DC–DC Converters for Both High and Low Step-Ratio Connections in MVDC Distribution Systems

Xiang

Qiao

et al. 2021

IEEE Trans. Power Electron.

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DC transformers based on power electronics are key items of equipment for medium voltage dc (MVDC) distribution systems. Both high and low step-ratio dc-dc conversions are required to interface dc links at different voltages to form an integrated dc distribution system. The transformer-coupled resonant modular multilevel dc-dc converter (RMMC) is wellsuited to high step-ratio connection between a MVDC network and a low voltage dc (LVDC) network but it is not suitable in low stepratio conversion for linking two MVDC networks with similar but not identical voltages. This paper presents a circuit evolution of the high step-ratio transformer-coupled RMMC into its low step-ratio transformer-less RMMC counterpart. These two RMMCs share the same structure and the same resonant process within the resonant SM stack (RSS) giving rise to the same operational advantages. Also, the circuit design experience can be readily transferred from one to the other. From these two base RMMC circuits, a family of RMMCs with further configurations is elaborated that provide a wider variety of connection options for MVDC distribution systems. In this circuit family, each high step-ratio transformer-coupled RMMC has a low step-ratio transformer-less RMMC counterpart and one can be transformed into the other via the circuit evolution process presented. The theoretical analysis for both high and low stepratio RMMCs has been verified through full-scale simulations of medium voltage examples and further verified through downscaled experiments on laboratory prototypes.

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Section: Low Step-ratio Rmmcmentioning

confidence: 99%