The full-bridge modular multilevel converter (MMC) has attracted extensive attention due to its DC fault ride through capability, however, the greater number of switching devices in the full-bridge submodule (FBSM) poses a huge challenge to the operational reliability of the MMC. To cope with this problem, this article first proposes a switching se-quence (SS) method based on the full-bridge MMC by adding a switched-out state, all types of IGBT open-circuit faults can be reflected without additional switching loss. Further, this article analyzes the fault characteristic under the proposed SS switching method and propose a IGBT open-circuit fault diagnosis strategy. In the proposed fault diagnosis strategy, detects and faults are detected and all faulty SMs are located by judging whether the switching sequence count exceeds the threshold, and further the faulty type is distinguished through the polarity of the SS count and the change of the capac-itor voltage. The proposed fault diagnosis strategy can accurately detect the IGBT open-circuit faults, locate the malfunctioning SMs and indentify the faulty type, which is beneficial to active operation and maintenance. In addition, the proposed strategy does not require additional hardware and can diagnose all the faults correctly within one power fre-quency period (20 ms). Finally, the effectiveness of the proposed SS switching method and IGBT open-circuit fault diagnosis strategy is verified by hardware-in-the-loop platform.
关键词
模块化多电平换流器/全桥子模块/开路故障诊断/开关序列/故障类型/开关损耗
Key words
modular multilevel converter/full bridge submodule/open-circuit fault diagnosis/switching sequence/faulty type/switching loss
维普
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