A new modular multilevel converter for medium voltage high power oil &amp; gas motor drive applications

Advantages of the modular multilevel converter (MMC) such as modularity, scalability, fault-tolerant ability, low device switching frequency, transformerless grid connection etc. have made it the most promising converter topology for medium-tohigh-voltage, high-power applications. However, in MMC-based medium-voltage drives, the excessive fundamental-frequency submodule capacitor voltage ripple at low speeds or start-up poses a major technological challenge. A lot of low-frequency ripple suppression methods have been proposed to address this problem. This study summarises the state of the art in this area and classifies these methods into three categories. The pros and cons of them are discussed. An in-depth analysis of these methods from a practical viewpoint is given. Some future research trends are also discussed.

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“…At high speeds, the method can be removed. Therefore, the injection methods are best suited for such applications [79, 80].…”

Section: Further Discussionmentioning

confidence: 99%

Review on low‐frequency ripple suppression methods for MMCs for medium‐voltage drive applications

Wang

Chen

Liao

et al. 2018

IET Power Electronics

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“…To ensure stable operation, the power on the AC side must be equal to the power on the DC side if losses are neglected. Therefore at least one of the freely adjustable currentsx f has to be a DC current to generate the power in combination with z 4 = V dc and to satisfy the branch energies according to (15). A constant value approach forx f (DC current for stationary operation) isx f = a 10 a 20 a 30 .…”

Section: ) Prerequisitesmentioning

confidence: 99%

“…The topology is also considered promising as galvanically isolated grid inverters [11], [12]. Furthermore, this topology also becomes increasingly popular as a drive converter [13]- [15] especially in the medium voltage range above 1 kV. The motor friendly behaviour of the MMC enables thereby efficient and reliable variable frequency drive solutions.…”

Section: Introductionmentioning

confidence: 99%

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Energy Pulsation Reduction in Modular Multilevel Converters Using Optimized Current Trajectories

Braeckle

Himmelmann

Gröll

et al. 2021

IEEE Open J. Power Electron.

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In power electronics, the modular multilevel converter (MMC) is an easily scalable topology with an high output voltage quality. It is suitable for the transmission of large amounts of electrical power over long distances, which supports the realization of the ongoing energy transition. State-of-the-art methods require a comparatively large total cell capacitance in the system for energy pulsations during operation. In the present paper, in order to minimize this total capacitance, first a new method is developed to model the system, and second, by help of this model, optimal current trajectories are calculated. These currents are used for control to reduce the energy pulsation over the complete operating range, and thus, to better utilize the hardware. The new method independent on the Clarke transformations is implemented on a laboratory scale setup, and measurement results are presented which validate the new method. Furthermore, the new method is compared to the state-of-the-art method of the compensation of the 2nd harmonic and outperforms the latter significantly. This applies to the entire operating range for different power factors. A total reduction of up to 44% of the energy pulsations is achieved.

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“…The Modular Multilevel Converter (MMC) provides several advantages such as high voltage ratings, high power quality, modularity, and transformerless operation, making it attractive for medium-and high-voltage power conversion applications [1][2][3][4]. The MMC is already employed in high-voltage DC transmission [5][6][7][8], photovoltaic power plants [9,10], and medium-voltage motor applications [11].…”

Section: Introductionmentioning

confidence: 99%

Pareto Frontier of the Arm Energy Ripple and the Conduction Losses of a Modular Multilevel Converter

López¹,

Fehr²,

Pérez³

et al. 2021

Energies

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Modular multilevel converters can achieve high power quality and voltage ratings, becoming a good alternative for high-voltage direct-current applications. However, the circulating current and capacitor voltage ripple remain significant drawbacks, mainly due to the impact on efficiency and power density. In this work, a stationary operation of a modular multilevel converter is optimized by calculating the Pareto frontier of the arm energy ripple and the conduction losses for different operating conditions. From the set of optimal solutions, the best trade-off between energy ripple and power losses can be chosen depending on the application requirements. Therefore, an optimal operating point regarding capacitor voltage ripple and circulating current was found, optimizing efficiency and allowing a reduction of capacitance, hence size and cost. The theoretical analysis and results are validated experimentally on a prototype test-bench.

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A new modular multilevel converter for medium voltage high power oil & gas motor drive applications

Cited by 24 publications

References 3 publications

Review on low‐frequency ripple suppression methods for MMCs for medium‐voltage drive applications

Review on low‐frequency ripple suppression methods for MMCs for medium‐voltage drive applications

Energy Pulsation Reduction in Modular Multilevel Converters Using Optimized Current Trajectories

Pareto Frontier of the Arm Energy Ripple and the Conduction Losses of a Modular Multilevel Converter

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