Abstract:V-clamp multilevel converter (VMC) with the energy buffer capacitor only in common DC bank is suitable for the medium-voltage and high-power applications. However, stray inductance in the current transition loop of VMC may result in the turn-off over-voltage of the IGBT. To address this problem, this paper proposes a simple and practical snubber for VMC. Based on the operation modes of VMC, the switches are classified into main switches and auxiliary switches. The main switch operates and switches the current path, and a snubber capacitor is added across each pair of complementary main switches (i.e. half-bridge switching buffer alike unit) to suppress the turn-off transient over-voltage. The auxiliary switch is turned on first and then turned off after the switching time of the corresponding main switch, and only provides the static blocking voltage and does not need dynamic over-voltage protection. A seven-level VMC is taken as an example to verify this strategy. The experimental results show that the proposed snubber circuit can effectively reduce the turn-off transient voltage of the IGBT in VMC, and only needs a small amount of snubber capacitors for main switches to form half-bridge switching buffer alike units. It has low cost, high reliability and good engineering practicability.
薛尧, 王琛琛, 杨晓峰, 李凯, 郑琼林. 一种用于V形钳位多电平变换器的IGBT吸收电路方案[J]. 电工技术学报, 2022, 37(14): 3608-3619.
Xue Yao, Wang Chenchen, Yang Xiaofeng, Li Kai, Zheng Trillion Q. Research on an IGBT Snubber Circuit for the V-clamp Multilevel Converter. Transactions of China Electrotechnical Society, 2022, 37(14): 3608-3619.
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