Leg-Balancing Control of the DC-link Voltage for Modular Multilevel Converters

Sixing Du; Jinjun Liu; Jiliang Lin

Leg-Balancing Control of the DC-link Voltage for Modular Multilevel Converters

Sixing Du

Jinjun Liu

Jiliang Lin

Vol. 12, No. 5, pp. 739-747, Sep. 2012

10.6113/JPE.2012.12.5.739

DC-Link Voltage Control

MMC

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Abstract

This paper applies carrier phase shifted pulse-width modulation (CPS-PWM) to transformerless modular multilevel converters (MMC) to improve the output spectrum. Because the MMC topology is characterized by the double-star connection of six legs consisting of cascaded modular chopper cells with floating capacitors, the balance control of the DC-link capacitor voltage is essential for safe operation. This paper presents a leg-balancing control strategy to achieve DC-link voltage balance under all operating conditions. This strategy based on circulating current decoupling control focused on DC-link balancing between the upper and lower legs in each phase pair by considering the six legs as three independent phase-pairs. Experiments are implemented on a 100-V 3-kVA downscaled prototype. The experimental results show that the proposed leg-balancing control is both effective and practical.

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Cite this article

[IEEE Style]

S. Du, J. Liu, J. Lin, "Leg-Balancing Control of the DC-link Voltage for Modular Multilevel Converters," Journal of Power Electronics, vol. 12, no. 5, pp. 739-747, 2012. DOI: 10.6113/JPE.2012.12.5.739.

[ACM Style]

Sixing Du, Jinjun Liu, and Jiliang Lin. 2012. Leg-Balancing Control of the DC-link Voltage for Modular Multilevel Converters. Journal of Power Electronics, 12, 5, (2012), 739-747. DOI: 10.6113/JPE.2012.12.5.739.