A nearest level PWM method for the MMC in DC distribution grids

Yi Wang; Can  Hu; Ruoyu  Ding; Lie Xu; Chao  Fu; Erlin  Yang

doi:10.1109/TPEL.2018.2792148

A nearest level PWM method for the MMC in DC distribution grids

Yi Wang, Can Hu, Ruoyu Ding, Lie Xu, Chao Fu, Erlin Yang

Electronic And Electrical Engineering

Research output: Contribution to journal › Article › peer-review

135 Citations (Scopus)

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Abstract

For modular multilevel converters (MMCs) applied to medium-voltage DC distribution grids, using the traditional Nearest Level Modulation (NLM) as in HVDC systems can lead to severe current distortion due to significantly reduced module number. This paper proposes a hybrid modulation method combining NLM and Pulse Width Modulation (PWM) where only one module per arm operates under PWM mode. The proposed Nearest Level PWM (NL-PWM) method not only significantly reduces the current distortion, but also avoids the complicated voltage balancing control in each module. The harmonic characteristics of NL-PWM are derived using double Fourier transform, which provides theoretical basis for selecting module number and switching frequency for medium-voltage application in accordance with grid harmonic requirements. Finally, the harmonic characteristics and feasibility of the proposed modulation method are validated by simulation and experimental studies on a MMC with 6 modules per arm. The simulated and experimental results reveal that NL-PWM has better voltage and current harmonic characteristics over NLM and CPS-PWM, thereby suiting the application of MMC with few models.

Original language	English
Number of pages	17
Journal	IEEE Transactions on Power Electronics
Early online date	11 Jan 2018
DOIs	https://doi.org/10.1109/TPEL.2018.2792148
Publication status	E-pub ahead of print - 11 Jan 2018

Keywords

harmonic analysis
pulse width modulation
voltage control
power system harmonics

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Wang-etal-IEEE-TOPE-2018-A-nearest-level-PWM-method-for-the-MMCAccepted author manuscript, 1.61 MB

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title = "A nearest level PWM method for the MMC in DC distribution grids",

abstract = "For modular multilevel converters (MMCs) applied to medium-voltage DC distribution grids, using the traditional Nearest Level Modulation (NLM) as in HVDC systems can lead to severe current distortion due to significantly reduced module number. This paper proposes a hybrid modulation method combining NLM and Pulse Width Modulation (PWM) where only one module per arm operates under PWM mode. The proposed Nearest Level PWM (NL-PWM) method not only significantly reduces the current distortion, but also avoids the complicated voltage balancing control in each module. The harmonic characteristics of NL-PWM are derived using double Fourier transform, which provides theoretical basis for selecting module number and switching frequency for medium-voltage application in accordance with grid harmonic requirements. Finally, the harmonic characteristics and feasibility of the proposed modulation method are validated by simulation and experimental studies on a MMC with 6 modules per arm. The simulated and experimental results reveal that NL-PWM has better voltage and current harmonic characteristics over NLM and CPS-PWM, thereby suiting the application of MMC with few models.",

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author = "Yi Wang and Can Hu and Ruoyu Ding and Lie Xu and Chao Fu and Erlin Yang",

note = "(c) 2018 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.",

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T1 - A nearest level PWM method for the MMC in DC distribution grids

AU - Wang, Yi

AU - Hu, Can

AU - Ding, Ruoyu

AU - Xu, Lie

AU - Fu, Chao

AU - Yang, Erlin

N1 - (c) 2018 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.

PY - 2018/1/11

Y1 - 2018/1/11

N2 - For modular multilevel converters (MMCs) applied to medium-voltage DC distribution grids, using the traditional Nearest Level Modulation (NLM) as in HVDC systems can lead to severe current distortion due to significantly reduced module number. This paper proposes a hybrid modulation method combining NLM and Pulse Width Modulation (PWM) where only one module per arm operates under PWM mode. The proposed Nearest Level PWM (NL-PWM) method not only significantly reduces the current distortion, but also avoids the complicated voltage balancing control in each module. The harmonic characteristics of NL-PWM are derived using double Fourier transform, which provides theoretical basis for selecting module number and switching frequency for medium-voltage application in accordance with grid harmonic requirements. Finally, the harmonic characteristics and feasibility of the proposed modulation method are validated by simulation and experimental studies on a MMC with 6 modules per arm. The simulated and experimental results reveal that NL-PWM has better voltage and current harmonic characteristics over NLM and CPS-PWM, thereby suiting the application of MMC with few models.

AB - For modular multilevel converters (MMCs) applied to medium-voltage DC distribution grids, using the traditional Nearest Level Modulation (NLM) as in HVDC systems can lead to severe current distortion due to significantly reduced module number. This paper proposes a hybrid modulation method combining NLM and Pulse Width Modulation (PWM) where only one module per arm operates under PWM mode. The proposed Nearest Level PWM (NL-PWM) method not only significantly reduces the current distortion, but also avoids the complicated voltage balancing control in each module. The harmonic characteristics of NL-PWM are derived using double Fourier transform, which provides theoretical basis for selecting module number and switching frequency for medium-voltage application in accordance with grid harmonic requirements. Finally, the harmonic characteristics and feasibility of the proposed modulation method are validated by simulation and experimental studies on a MMC with 6 modules per arm. The simulated and experimental results reveal that NL-PWM has better voltage and current harmonic characteristics over NLM and CPS-PWM, thereby suiting the application of MMC with few models.

KW - harmonic analysis

KW - pulse width modulation

KW - voltage control

KW - power system harmonics

UR - http://ieeexplore.ieee.org/document/8253885/

U2 - 10.1109/TPEL.2018.2792148

DO - 10.1109/TPEL.2018.2792148

M3 - Article

SN - 0885-8993

JO - IEEE Transactions on Power Electronics

JF - IEEE Transactions on Power Electronics

ER -

A nearest level PWM method for the MMC in DC distribution grids

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Keywords

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