An Improved Pulse Width Modulation Method for Chopper-Cell-Based Modular Multilevel Converters

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

doi:10.1109/tpel.2012.2187800

Cited by 229 publications

(100 citation statements)

References 14 publications

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“…Therefore, some techniques are proposed to improve the performance of NLM methods in case of a small number of SMs [19]- [22]. By combining NLM and PWM, the submodule unified PWM (SUPWM) [19] and the improved SUPWM [20] can generate an output voltage with a high quality. However, the switching frequency of the IGBTs is increased when compared to NLM.…”

Section: Introductionmentioning

confidence: 99%

A Hybrid Modular Multilevel Converter Topology with an Improved Nearest Level Modulation Method

Wang¹,

Han²,

Bai³

2017

Journal of Power Electronics

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In this paper, a hybrid modular multilevel converter (MMC) topology with an improved nearest level modulation method is proposed for medium-voltage high-power applications. The arm of the proposed topology contains N series connected half-bridge submodules (HBSMs), one full-bridge submodule (FBSM) and an inductor. By exploiting the FBSM, half-level voltages are obtained in the arm voltages. Therefore, an output voltage with a 2N+1 level number can be generated. Moreover, the total level number of the inserted submodules (SMs) is a constant. Thus, there is no pulse voltage across the arm inductors, and the SM capacitor voltage is rated. With the proposed voltage balancing method, the capacitor voltage of the HBSM is twice the voltage of the FBSM, and each IGBT of the FBSM has a relatively low switching frequency and an equalized conduction loss. The capacitor voltage balancing methods of the two kinds of SMs are implemented independently. As a result, the switching frequency of the HBSM is not increased compared to the conventional MMC. In addition, according to a theoretical calculation of the total harmonic distortion of the electromotive force (EMF), the voltage quality with the presented method can be significantly enhanced when the SM number is relatively small. Simulation and experimental results obtained with a MMC-based inverter verify the validity of the developed method.

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Section: Introductionmentioning

confidence: 99%

A Hybrid Modular Multilevel Converter Topology with an Improved Nearest Level Modulation Method

Wang¹,

Han²,

Bai³

2017

Journal of Power Electronics

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“…Because the capacitor voltage balancing should be the most basic yet critical functionality of the MMC, various balancing techniques of the capacitor voltage have been discussed in [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]. Reference [1] deals with two types of pulse width modulated MMC (PWM-MMC), focusing on their circuit configurations and voltage balancing control.…”

Section: Introductionmentioning

confidence: 99%

“…Closed loop control for the submodule voltage balancing is introduced with Carrier Phase Shifted Pulse Width Modulation (CPSPWM) in [8] and [9]. The submodule capacitor voltage balancing with phase disposition PWM (PDPWM) for MMC is used in [10][11][12][13]. The submodule capacitor voltages within each arm are measured and sorted, and the number of submodules to be switched on/off is determined.…”

Section: Introductionmentioning

confidence: 99%

Trade-Off Strategies in Designing Capacitor Voltage Balancing Schemes for Modular Multilevel Converter HVDC

Nam¹,

Kim²,

Kim³

et al. 2016

Journal of Electrical Engineering and Technology

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-This paper focuses on the engineering trade-offs in designing capacitor voltage balancing schemes for modular multilevel converters (MMC) HVDC: regulation performance and switching loss. MMC is driven by the on/off switch operation of numerous submodules and the key design concern is balancing submodule capacitor voltages minimizing switching transition among submodules because it represents the voltage regulation performance and system loss. This paper first introduces the state-ofthe-art MMC-HVDC submodule capacitor voltage balancing methods reported in the literatures and discusses the trade-offs in designing these methods for HVDC application. This paper further proposes a submodule capacitor balancing scheme exploiting a control signal to flexibly interchange between the on-state and the off-state submodules. The proposed scheme enables desired performance-based voltage regulation and avoids unnecessary switching transitions among submodules, consequently reducing the switching loss. The flexibility and controllability particularly fit in high-level MMC HVDC applications where the aforementioned design trade-offs become more crucial. Simulation studies for MMC HVDC are performed to demonstrate the validity and effectiveness of the proposed capacitor voltage balancing algorithm.

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“…MMC-HVDC has a lot more advantages than two-level or three-level VSC-HVDCs, such as lower harmonic components at the Alternating Current (AC) side of the converter [4], greater reduction of the switching frequency, fewer losses [5] and operation consistency for the switching devices in series in an arm is not necessary [6]. There has been extensive research on MMC systems, and most of this research has been concentrated on mathematical modeling [7]- [9], modulation mode [10]- [12], and control strategies [13]- [16]. Physical verification plays an important role in testing control devices, planning the primary system and engineering operation, since it is closer to the practical project.…”

Section: Introductionmentioning

confidence: 99%

“…Most of the physical primary systems mentioned in the existing literature are for 2 to 17 levels [12], [17]- [19]. In [20]- [21], 40 to 49 level prototypes drastically improve the ability of physical verification, while this achievement is based on reductions of the voltage value.…”

Section: Introductionmentioning

confidence: 99%

A Hardware-in-the-loop Platform for Modular Multilevel Converter Simulations

Liu¹,

Tian²,

Wang³

et al. 2016

Journal of Power Electronics

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In this paper, a hardware-in-the-loop simulation platform for MMCs is established, which connects a real time digital simulator (RTDS) and a designed MMC controller with optical fiber. In this platform, the converter valves are simulated with a small time step of 2.5 microsecond in the RTDS, and multicore technology is implemented for the controller so that the parallel valve control is distributed between different cores. Therefore, the designed controller can satisfy the requirements of real-time control. The functions of the designed platform and the rationality for the designed controller are verified through experimental tests. The results show that different modulation modes and various control strategies can be implemented in the simulation platform and that each control objective can been tracked accurately and with a fast dynamic response.

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An Improved Pulse Width Modulation Method for Chopper-Cell-Based Modular Multilevel Converters

Cited by 229 publications

References 14 publications

A Hybrid Modular Multilevel Converter Topology with an Improved Nearest Level Modulation Method

A Hybrid Modular Multilevel Converter Topology with an Improved Nearest Level Modulation Method

Trade-Off Strategies in Designing Capacitor Voltage Balancing Schemes for Modular Multilevel Converter HVDC

A Hardware-in-the-loop Platform for Modular Multilevel Converter Simulations

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