Capacitor voltage balancing method for hybrid modular multilevel converters based on second‑harmonic voltage injection

Hongxu Li; Qin Wang; Qunfang Wu; Lan Xiao; Jinbo Li

Capacitor voltage balancing method for hybrid modular multilevel converters based on second‑harmonic voltage injection

Vol. 24, No. 4, pp. 553-564, Apr. 2024

10.1007/s43236-023-00752-7

Capacitor voltage balance

Hybrid modular multilevel converter

Boosted modulation index

Second-harmonic voltage injection

Abstract

Due to different output voltages, capacitor voltage imbalance occurs between half-bridge sub-modules (HBSM) and fullbridge sub-modules (FBSM) in hybrid modular multilevel converters (MMCs) under a boosted modulation index (m). To address this issue, a capacitor voltage balancing method based on second-harmonic voltage injection is proposed in this paper. The mechanism of the proposed method is to eliminate the DC component in the charging power of sub-modules under the restriction that the HBSM cannot output negative voltage. The proposed method is divided into two cases according to m. Case 1 is used when m ≤ 1.4, while Case 2 is implemented when m > 1.4. When compared with similar capacitor voltage balancing methods, the proposed SVI method has a simpler structure that can greatly reduce the number of computations. Simulation and experimental results verify the effectiveness of the proposed capacitor voltage balancing method.

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Cite this article

[IEEE Style]

H. Li, Q. Wang, Q. Wu, L. Xiao, J. Li, "Capacitor voltage balancing method for hybrid modular multilevel converters based on second‑harmonic voltage injection," Journal of Power Electronics, vol. 24, no. 4, pp. 553-564, 2024. DOI: 10.1007/s43236-023-00752-7.

[ACM Style]

Hongxu Li, Qin Wang, Qunfang Wu, Lan Xiao, and Jinbo Li. 2024. Capacitor voltage balancing method for hybrid modular multilevel converters based on second‑harmonic voltage injection. Journal of Power Electronics, 24, 4, (2024), 553-564. DOI: 10.1007/s43236-023-00752-7.