A single-phase to three-phase direct AC/AC modular multilevel cascade converter based on double-star bridge-cells (MMCC-DSBC)

Thitichaiworakorn, Nuntawat; Hagiwara, Makoto; Akagi, Hirofumi

doi:10.1109/ifeec.2013.6687553

Cited by 20 publications

(7 citation statements)

References 13 publications

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“…By substituting ( 23) into (24), and by remembering that V CE(sat) = 2 V and I AC = 100 A, the value obtained for the MMC conduction losses is equal to:…”

Section: Conduction Lossesmentioning

confidence: 99%

New AC–AC Modular Multilevel Converter Solution for Medium-Voltage Machine-Drive Applications: Modular Multilevel Series Converter

et al. 2020

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Due to its scalability, reliability, high power quality and flexibility, the modular multilevel converter is the standard solution for high-power high-voltage applications in which an AC–DC–AC connection is required such as high-voltage direct-current transmission systems. However, this converter presents some undesired features from both structural and operational perspectives. For example, it presents a high number of components, which results in high costs, size, weight and conduction losses. Moreover, the modular multilevel converter presents problems dealing with DC-side faults, with unbalanced grid conditions, and many internal control loops are required for its proper operation. In variable-frequency operation, the modular multilevel converter presents some serious limitations. The most critical are the high-voltage ripples, in the submodule capacitors, at low frequencies. Thus, many different AC–AC converter solutions, with modular multilevel structure, have been proposed as alternatives for high-power machine-drive applications such as offshore wind turbines, pumped-hydro-storage systems and industrial motor drives. These converters present their own drawbacks mostly related to control complexity, operational limitations, size and weight. This paper introduces an entirely new medium-voltage AC–AC modular multilevel converter solution with many operational and structural advantages in comparison to the modular multilevel converter and other alternative topologies. The proposed converter presents high performance at low frequencies, regarding the amplitude of the voltage ripples in the submodule capacitors, which could make it very suitable for machine-drive applications. In this paper, an analytical description of the voltage ripples in the submodule capacitors is proposed, which proves the high performance of the converter under low-frequency operation. Moreover, the proposed converter presents high performance under unbalanced grid conditions. This important feature is demonstrated through simulation results. The converter solution introduced in this paper has a simple structure, with decoupled phases, which leads to the absence of undesired circulating currents and to a straightforward control, with very few internal control loops for its proper operation, and with simple modulation. Since the converter phases are decoupled, no arm inductors are required, which contributes to the weight and size reduction of the topology. In this paper, a detailed comparison analysis with the modular multilevel converter is presented based on number of components, conduction and switching losses. This analysis concludes that the proposed converter solution presents a reduction in costs and an expressive reduction in size and weight, in comparison to the modular multilevel converter. Thus, it should be a promising solution for high-power machine-drive applications that require compactness and lightness such as offshore wind turbines. In this paper, simulation results are presented explaining the behavior of the proposed converter, proving that it is capable of synthesizing a high-power-quality load voltage, with variable frequency, while exchanging power with the grid. Thus, this topology could be used to control the machine speed in a machine-drive application. Finally, experimental results are provided to validate the topology.

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“…By substituting ( 23) into (24), and by remembering that V CE(sat) = 2 V and I AC = 100 A, the value obtained for the MMC conduction losses is equal to:…”

Section: Conduction Lossesmentioning

confidence: 99%

New AC–AC Modular Multilevel Converter Solution for Medium-Voltage Machine-Drive Applications: Modular Multilevel Series Converter

et al. 2020

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“…A control scheme based on capacitor voltage estimation is proposed in [11]. The converter operation focusing on wind turbine generation systems are analyzed in [12]. A study on how the energy variations can be reduced by an appropriate choice of voltage ratio is presented in [13].…”

Section: Introductionmentioning

confidence: 99%

Control and Admittance Modeling of an AC/AC Modular Multilevel Converter for Railway Supplies

Bessegato

Ilves

Harnefors

et al. 2020

IEEE Trans. Power Electron.

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Control and Admittance Modeling of an AC/AC Modular Multilevel Converter for Railway Supplies IEEE transactions on power electronicsAccess to the published version may require subscription. N.B. When citing this work, cite the original published paper. Permanent link to this version:Abstract-Modular multilevel converters (MMCs) can be configured to perform ac/ac conversion, which makes them suitable as railway power supplies. In this paper, a hierarchical control scheme for ac/ac MMCs for railway power supplies is devised and evaluated, considering the requirements and the operating conditions specific to this application. Furthermore, admittance models of the ac/ac MMC are developed, showing how the suggested hierarchical control scheme affects the three-phase and the single-phase side admittances of the converter. These models allow for analyzing the stability of the interconnected system using the impedance-based stability criterion and the passivitybased stability assessment. Finally, the findings presented in this paper are validated experimentally, using a down-scaled MMC.

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“…The criteria for designing the MMSC input-terminal voltage is presented in (38), which states that the voltage imposed to the MMSC input terminals should be equal or greater than two times the amplitude of the load-voltage reference. Let us now consider the situation where the third phase of the grid (phase C) is also available in the second illustrative example in a way that the illustrative example shown in Fig.…”

Section: Comparative Analysis In Terms Of Component Count and Power R...mentioning

confidence: 99%

“…Various converter solutions with a modular multilevel structure have been proposed in the literature as alternatives for AC-AC applications [14,[30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48], and some of them specifically for high-power medium-voltage electrical-machine drives [7,8,14,15,30,32,35,[39][40][41][42]48]. These topologies are proposed to overcome drawbacks of the MMC such as its high component count (which results in high costs, volume and weight) but especially to overcome the MMC poor performance at low frequencies regarding its excessive submodule-capacitor voltage ripple.…”

Section: Introduction 1backgroundmentioning

confidence: 99%

Novel Converter Solutions with a Modular Multilevel Structure for High-Power Medium-Voltage Electrical Machine Drive Applications

Gontijo¹

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A single-phase to three-phase direct AC/AC modular multilevel cascade converter based on double-star bridge-cells (MMCC-DSBC)

Cited by 20 publications

References 13 publications

New AC–AC Modular Multilevel Converter Solution for Medium-Voltage Machine-Drive Applications: Modular Multilevel Series Converter

New AC–AC Modular Multilevel Converter Solution for Medium-Voltage Machine-Drive Applications: Modular Multilevel Series Converter

Control and Admittance Modeling of an AC/AC Modular Multilevel Converter for Railway Supplies

Novel Converter Solutions with a Modular Multilevel Structure for High-Power Medium-Voltage Electrical Machine Drive Applications

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