Modeling, Analysis, and Enhanced Control of Modular Multilevel Converters with Asymmetric Arm Impedance for HVDC Applications

Peng Dong; Jing Lyu; Xu Cai

Modeling, Analysis, and Enhanced Control of Modular Multilevel Converters with Asymmetric Arm Impedance for HVDC Applications

Peng Dong

Jing Lyu

Xu Cai

Vol. 18, No. 6, pp. 1683-1696, Nov. 2018

10.6113/JPE.2018.18.6.1683

Asymmetric arm impedance

Capacitor voltage balance

Control

Modular multilevel converter (MMC)

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Abstract

Under the conventional control strategy, the asymmetry of arm impedances may result in the poor operating performance of modular multilevel converters (MMCs). For example, fundamental frequency oscillation and double frequency components may occur in the dc and ac sides, respectively; and submodule (SM) capacitor voltages among the arms may not be balanced. This study presents an enhanced control strategy to deal with these problems. A mathematical model of an MMC with asymmetric arm impedance is first established. The causes for the above phenomena are analyzed on the basis of the model. Subsequently, an enhanced current control with five integrated proportional integral resonant regulators is designed to protect the ac and dc terminal behavior of converters from asymmetric arm impedances. Furthermore, an enhanced capacitor voltage control is designed to balance the capacitor voltage among the arms with high efficiency and to decouple the ac side control, dc side control, and capacitor voltage balance control among the arms. The accuracy of the theoretical analysis and the effectiveness of the proposed enhanced control strategy are verified through simulation and experimental results.

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Cite this article

[IEEE Style]

P. Dong, J. Lyu, X. Cai, "Modeling, Analysis, and Enhanced Control of Modular Multilevel Converters with Asymmetric Arm Impedance for HVDC Applications," Journal of Power Electronics, vol. 18, no. 6, pp. 1683-1696, 2018. DOI: 10.6113/JPE.2018.18.6.1683.

[ACM Style]

Peng Dong, Jing Lyu, and Xu Cai. 2018. Modeling, Analysis, and Enhanced Control of Modular Multilevel Converters with Asymmetric Arm Impedance for HVDC Applications. Journal of Power Electronics, 18, 6, (2018), 1683-1696. DOI: 10.6113/JPE.2018.18.6.1683.