Fault-tolerant control strategy plays a significant role in improving the reliability of three-level T-type inverter where fault diagnosis method is the key and a research hotspot. Load power factor variation and modulation index regulation have great effect on conventional load current based diagnosis methods. Therefore, this article proposes a novel voltage vector based method for single-switch open-circuit fault diagnosis in three-level T-type inverter. Average output voltage vector calculated by voltages between dc-link neutral-point and bridge output terminals is taken as the eigenvector in the procedure and failed switch can be located by three diagnosis variables including angle of eigenvector, normalized modulus of eigenvector, and neutral-point potential. These variables will be some certain values under circuit fault, which are defined as eigenvalues. The vector trajectory prediction technology is utilized for threshold setting, by which the diagnosis is suitable for different power factors and different modulation indices. The strategy of redundant vector replacement is applied to realize fault-tolerant operation and verifying the proposed scheme. Simulations and experiments are carried out to illustrate the superiorities of the proposal.

中文翻译：

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基于平均电压矢量的三电平T型逆变器单开关开路诊断方法

容错控制策略对提高三电平T型逆变器的可靠性具有重要作用，其中故障诊断方法是关键和研究热点。负载功率因数变化和调制指数调节对传统的基于负载电流的诊断方法有很大影响。因此，本文提出了一种基于电压矢量的新型三电平T型逆变器单开关开路故障诊断方法。过程中以直流母线中性点与桥输出端电压计算的平均输出电压向量作为特征向量，通过特征向量角度、特征向量归一化模数和中性点三个诊断变量可以定位故障开关潜在的。这些变量在电路故障下会是一些特定的值，它们被定义为特征值。采用矢量轨迹预测技术进行阈值设置，适用于不同功率因数和不同调制指数的诊断。应用冗余向量替换策略实现容错操作并验证了所提出的方案。进行了模拟和实验以说明该提议的优越性。