A comparison of modular multilevel energy conversion processes: DC/AC versus DC/DC

Kish, Gregory J.; Lehn, Peter W.

doi:10.1109/ipec.2014.6869702

Cited by 17 publications

(11 citation statements)

References 13 publications

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“…Recently, the modular dc/dc converter topology of Fig. 12 a was proposed [115, 116]. It generates output voltages that contain ac plus dc bias at the nodes ( p 1 , p 2 and p 3 ) and ( n 1 , n 2 and n 3 ) relative to ground.…”

Section: Review Of Established and Emerging Dc–dc Converter Topologiesmentioning

confidence: 99%

Review of dc–dc converters for multi‐terminal HVDC transmission networks

Adam

Gowaid

Finney

et al. 2016

IET Power Electronics

159

105

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This paper presents a comprehensive review of high-power dc-dc converters for high-voltage direct current (HVDC) transmission systems, with emphasis on the most promising topologies from established and emerging dc-dc converters.Additionally, it highlights the key challenges of dc-dc converter scalability to HVDC applications, and narrows down the desired features for high-voltage dc-dc converters, considering both device and system perspectives. Attributes and limitations of each dc-dc converter considered in this study are explained in detail and supported by time-domain simulations. It is found that the front-to-front quasi two-level operated modular multilevel converter, transition arm modular converter and controlled transition bridge converter offer the best solutions for high-voltage dc-dc converters that do not compromise galvanic isolation and prevention of dc fault propagation within the dc network. Apart from dc fault response, the MMC dc auto transformer and the transformerless hybrid cascaded two-level converter offer the most efficient solutions for tapping and dc voltage matching of multi-terminal HVDC networks. Key words:High-voltage dc-dc converter; modular multilevel converter; multi-terminal high-voltage dc networks; and prevention of dc faults propagation.I.

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Section: Review Of Established and Emerging Dc–dc Converter Topologiesmentioning

confidence: 99%

Review of dc–dc converters for multi‐terminal HVDC transmission networks

Adam

Gowaid

Finney

et al. 2016

IET Power Electronics

159

105

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“…The M2dc is attracting much interest from academia and industry for HVdc systems, e.g., [23], [24]. However, one fundamental limitation of the topology is that it experiences high ac current stresses in the arms when [22], [25], [26]. The ac current stresses go up as the dc input voltage is further stepped down, eventually rendering the topology impractical for certain applications, e.g., HVdc to MVdc interconnects or HVdc power tapping.…”

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confidence: 99%

The Modular Multilevel DC Converter With Inherent Minimization of Arm Current Stresses

Kish

2020

IEEE Trans. Power Electron.

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The modular multilevel dc converter (M2dc) is a partial power processing dc-dc converter that is gaining popularity for medium-voltage and high-voltage dc (HVdc) grid applications. However, internal ac current stresses go up as the step-down dc voltage ratio increases, leading to increased cost and losses, and ultimately renders the M2dc impractical for some applications. The HVdc autotransformer (AT) (HVdc-AT) is another class of the partial power processing dc-dc converter that circumvents this issue by using a transformer for interarm ac voltage matching, although the core must tolerate a very large dc voltage stress between windings that leads to increased magnetics size and weight. Interestingly, the M2dc does not suffer from interwinding dc voltage stresses. This article presents a new class of the partial power processing dc-dc converter that uses an integrated center-tapped transformer to merge the best traits of the M2dc and HVdc-AT. Comparative analysis reveals the proposed converter can minimize ac current stresses at all operating points while also achieving a significant reduction in transformer area product relative to the HVdc-AT. A dynamic controller is proposed that regulates dc power transfer while ensuring balanced capacitor voltages. The converter operation and dynamic controls are validated by simulation and experiment. Index Terms-DC-DC power conversion, HVdc converters, HVdc transmission. NOMENCLATURE CCL Circulating current loop. F2F-MMC Front-to-front modular multilevel converter. HVdc High-voltage dc. HVdc-AT High-voltage dc autotransformer. MMC Modular multilevel converter. MVdc Medium-voltage dc. M2dc Modular multilevel dc converter. M2dc-CT Modular multilevel dc converter with integrated center-tapped transformer. P3T Partial power processing transformer. SM Submodule. I. INTRODUCTION D C POWER transmission and distribution technology has been garnering increased attention over the last several Manuscript

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“…The stack volt-ampere rating expression for transformer-less front-to-front MMC RSP-FF [35], [36] and direct-chain-link MMC RSP-DL [25], [37] are given in (26) and (27) The detailed comparison result among these three dc-dc converters are presented in Fig. 4.…”

Section: A Requirement For Stack Semiconductor Volt-ampere Ratingmentioning

confidence: 99%

“…For a transformer-less front-to-front MMC or direct-chain-link MMC, the relevant energy deviation are expressed in (31) and (32) [33], [34], [37], where ∆ and ∆ denote the stack energy deviation sum in the low-voltage side and high-voltage side of the transformer-less front-to-front MMC, ∆ and ∆ are the stack energy deviation sum in the top arms and bottom arms of the direct-chain-link MMC. 5 compares the total stack energy deviation of three converters over one switching cycle at the same switching frequency and step-ratio.…”

Section: B Requirement For Stack Capacitive Energy Storagementioning

confidence: 99%

A Modular Multilevel DC–DC Converter With a Compact Sub-Module Stack Suited to Low Step Ratios

Xiang

Zhang

Chaffey

et al. 2019

IEEE Trans. Power Delivery

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The voltage ratings for dc transmission and distribution are not currently standardized because cable technology is advancing rapidly and therefore low step-ratio dc-dc converter at multi-megawatt scale is a crucial technology for combining point-to-point dc links into multi-terminal networks. This paper presents a modular multilevel dc-dc converter configuration with only a single stack of half-bridge sub-modules (SM) and a resonant tank. The power processed through the stack is a small fraction of the throughput power if the step-ratio is small (− ⁄). Detailed analysis shows the required semiconductor ratings are much smaller compared to the front-to-front MMC and modular converters derived from standard dc-dc topologies. Further, the requirement for SM capacitive energy storage is also significantly less than those converters. The theoretical analysis and the operating principles have been verified by full-scale simulation examples and experiments with a down-scaled prototype. The SMs are operated with an adjustable phase-shift to create a high frequency excitation across the resonant tank for further volume reduction. The SM capacitors self-balance without the need for switching pattern adjustments and the resonant operation provides soft-switching for all power switches to increase efficiency.

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A comparison of modular multilevel energy conversion processes: DC/AC versus DC/DC

Cited by 17 publications

References 13 publications

Review of dc–dc converters for multi‐terminal HVDC transmission networks

Review of dc–dc converters for multi‐terminal HVDC transmission networks

The Modular Multilevel DC Converter With Inherent Minimization of Arm Current Stresses

A Modular Multilevel DC–DC Converter With a Compact Sub-Module Stack Suited to Low Step Ratios

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