An Inner Current Suppressing Method for Modular Multilevel Converters

Li, Zixin; Wang, Ping; Chu, Zunfang; Zhu, Heyuan; Luo, Yan; Li, Yaohua

doi:10.1109/tpel.2013.2242204

Cited by 238 publications

(83 citation statements)

References 20 publications

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“…Due to the MMC's unique configuration, there are complex interactions involving different currents and voltages in the MMC, and extensive research has been conducted on the modeling and control strategy of the MMC [11][12][13][14][15][16][17][18][19][20][21][22]. The relationship between the arm current and capacitor voltage was analyzed in [11] and [12].…”

Section: Introductionmentioning

confidence: 99%

“…Many control strategies have been developed such as circulating current control [15][16][17][18] and energy-based modeling control [19][20][21][22]. The circulating current control method suppresses the even-order common-mode harmonic current by adding extra controllers, such as a proportional-integral (PI) controller in a double-frequency rotational frame [15], a series of resonant controllers tuned at even-order harmonic frequencies [16], or a repetitive controller [17][18]. The energy-based modeling control is based on the schemes of regulating the total energy and energy balancing [19][20][21][22][23].…”

Section: Introductionmentioning

confidence: 99%

“…Yao is with China Electric Power Research Institute, Xiaoying Road, Beijing, 100192, China (email: yaoliangzhong@epri.sgcc.com.cn) the MMC, affecting the capacitor voltage in the sub-modules (SM) and the energy variation in each arm, but it does not affect the ac side current (differential-mode current). Many control strategies have been developed such as circulating current control [15][16][17][18] and energy-based modeling control [19][20][21][22]. The circulating current control method suppresses the even-order common-mode harmonic current by adding extra controllers, such as a proportional-integral (PI) controller in a double-frequency rotational frame [15], a series of resonant controllers tuned at even-order harmonic frequencies [16], or a repetitive controller [17][18].…”

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confidence: 99%

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Analysis and Control of Modular Multilevel Converters under Asymmetric Arm Impedance Conditions

Zeng

Yao

et al. 2016

IEEE Trans. Ind. Electron.

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This version is available at https://strathprints.strath.ac.uk/54225/ Strathprints is designed to allow users to access the research output of the University of Strathclyde. Unless otherwise explicitly stated on the manuscript, Copyright © and Moral Rights for the papers on this site are retained by the individual authors and/or other copyright owners. Please check the manuscript for details of any other licences that may have been applied. You may not engage in further distribution of the material for any profitmaking activities or any commercial gain. You may freely distribute both the url (https://strathprints.strath.ac.uk/) and the content of this paper for research or private study, educational, or not-for-profit purposes without prior permission or charge.Any correspondence concerning this service should be sent to the Strathprints administrator: strathprints@strath.ac.ukThe Strathprints institutional repository (https://strathprints.strath.ac.uk) is a digital archive of University of Strathclyde research outputs. It has been developed to disseminate open access research outputs, expose data about those outputs, and enable the management and persistent access to Strathclyde's intellectual output. IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICSAbstract--This paper presents a detailed analysis and improved control strategy for Modular Multilevel Converters (MMC) under asymmetric arm inductance conditions. Unlike symmetric conditions, the fundamental ac current is not split equally between the upper and lower arms under asymmetric conditions, and the dc and double-frequency components in the common-mode current also flow into the ac side. To solve these issues, a theoretical analysis of the effect of asymmetric conditions on MMC operation is carried out using equivalent circuits at different frequencies. Three control targets are then presented to enhance the operational performance. A control strategy providing the control of differential-mode current, common-mode current and power balance is designed. The feasibility and validity of the proposed analysis and control strategy are demonstrated by simulation results from a threephase MMC system, and simulation and experimental results from a single-phase MMC system. Index Terms--Modular multilevel converter, differential-mode current, common-mode current, power balance, asymmetric conditions. I. INTRODUCTION1 HE modular multilevel converter (MMC) has drawn attention due to its advantages of modular design, high efficiency and scalability, and excellent output waveforms with low harmonic distortion [1][2][3][4][5][6][7][8][9][10].Due to the MMC's unique configuration, there are complex interactions involving different currents and voltages in the MMC, and extensive research has been conducted on the modeling and control strategy of the MMC [11][12][13][14][15][16][17][18][19][20][21][22]. The relationship between the arm current and capacitor voltage was analyzed in [11] and [12]. One of the special characteristics of the MMC is the common-mode current which usuall...

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

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Analysis and Control of Modular Multilevel Converters under Asymmetric Arm Impedance Conditions

Zeng

Yao

et al. 2016

IEEE Trans. Ind. Electron.

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“…1, each pole of an MMC consists of two arms, one on the top and the other on the bottom. Each arm consists of many SMs connected in series through a reactor [14], [15]. Each SM is a half-bridge circuit consisting of two IGBT switches and one DC capacitor.…”

Section: A MMC Power Circuitmentioning

confidence: 99%

A New Scheme for Nearest Level Control with Average Switching Frequency Reduction for Modular Multilevel Converters

Park¹,

Kim²,

Kim³

et al. 2016

Journal of Power Electronics

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This paper proposes a new NLC (Nearest Level Control) scheme for MMCs (Modular Multilevel Converters), which offers voltage ripple reductions in the DC capacitor of the SM (Sub-Module), the output voltage harmonics, and the switching losses. The feasibility of the proposed NLC was verified through computer simulations. Based on these simulation results, a hardware prototype of a 10kVA, DC-1000V MMC was manufactured in the lab. Experiments were conducted to verify the feasibility of the proposed NLC in an actual hardware environment. The experimental results were consistent with the results obtained from the computer simulations.

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“…Nevertheless, this rotated controller needs extra calculation for the coordinate transformations and cannot apply to unbalanced three-phase or single-phase systems. Further, multiple stationary-frame proportional resonant (PR) controllers have been adopted in [14] and [15] by attaching them to a traditional PI controller, and achieving an efficient gain by appropriately setting the resonant frequencies. Although this method is able to suppress the circulating current harmonics accurately, it is too complicated to design a series of multiple PR controllers since the circulating current contains too many harmonics such as the 2nd, 4th and 6th order harmonics.…”

Section: Introductionmentioning

confidence: 99%

Circulating Current Harmonics Suppression for Modular Multilevel Converters Based on Repetitive Control

Li¹,

Xu²,

Xu³

2014

Journal of Power Electronics

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Modular multilevel converters (MMCs) have emerged as the most promising topology for high and medium voltage applications for the coming years. However, one particular negative characteristic of MMCs is the existence of circulating current, which contains a dc component and a series of low-frequency even-order ac harmonics. If not suppressed, these ac harmonics will distort the arm currents, increase the power loses, and cause higher current stresses on the semiconductor devices. Repetitive control (RC) is well known due to its distinctive capabilities in tracking periodic signals and eliminating periodic errors. In this paper, a novel circulating current control scheme base on RC is proposed to effectively track the dc component and to restrain the low-frequency ac harmonics. The integrating function is inherently embedded in the RC controller. Therefore, the proposed circulating current control only parallels the RC controller with a proportional controller. Thus, conflicts between the RC controller and the traditional proportional integral (PI) controller can be avoided. The design methodologies of the RC controller and a stability analysis are also introduced. The validity of the proposed circulating current control approach has been verified by simulation and experimental results based on a three-phase MMC downscaled prototype.

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An Inner Current Suppressing Method for Modular Multilevel Converters

Cited by 238 publications

References 20 publications

Analysis and Control of Modular Multilevel Converters under Asymmetric Arm Impedance Conditions

Analysis and Control of Modular Multilevel Converters under Asymmetric Arm Impedance Conditions

A New Scheme for Nearest Level Control with Average Switching Frequency Reduction for Modular Multilevel Converters

Circulating Current Harmonics Suppression for Modular Multilevel Converters Based on Repetitive Control

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