Fault-Tolerant Control of Cascaded H-Bridge Converters Using Double Zero-Sequence Voltage Injection and DC Voltage Optimization


Vol. 14, No. 5, pp. 946-956, Sep. 2014
10.6113/JPE.2014.14.5.946


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 Abstract

Cascaded H-Bridge (CHB) converters can be directly connected to medium-voltage grids without using transformers and theypossess the advantages of large capacity and low harmonics. They are significant tools for providing grid connections inlarge-capacity renewable energy systems. However, the reliability of a grid-connected CHB converter can be seriouslyinfluenced by the number of power switching devices that exist in the structure. This paper proposes a fault-tolerant controlstrategy based on double zero-sequence voltage injection and DC voltage optimization to improve the reliability ofstar-connected CHB converters after one or more power units have been bypassed. By injecting double zero-sequence voltagesinto each phase cluster, the DC voltages of the healthy units can be rapidly balanced after the faulty units are bypassed. Inaddition, optimizing the DC voltage increases the number of faulty units that can be tolerated and improves the reliability of theconverter. Simulations and experimental results are shown for a seven-level three-phase CHB converter to validate the efficiencyand feasibility of this strategy.


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Cite this article

[IEEE Style]

Z. Ji, J. Zhao, Y. Sun, X. Yao, Z. Zhu, "Fault-Tolerant Control of Cascaded H-Bridge Converters Using Double Zero-Sequence Voltage Injection and DC Voltage Optimization," Journal of Power Electronics, vol. 14, no. 5, pp. 946-956, 2014. DOI: 10.6113/JPE.2014.14.5.946.

[ACM Style]

Zhendong Ji, Jianfeng Zhao, Yichao Sun, Xiaojun Yao, and Zean Zhu. 2014. Fault-Tolerant Control of Cascaded H-Bridge Converters Using Double Zero-Sequence Voltage Injection and DC Voltage Optimization. Journal of Power Electronics, 14, 5, (2014), 946-956. DOI: 10.6113/JPE.2014.14.5.946.