The increasing importance of cascaded H-bridge multilevel converters (CHBMCs) in high-power applications requires a higher priority to detect and protect against fault conditions. In this article, a current residual-based diagnosis scheme is proposed for the CHBMCs without additional sensors. On the premise of filtering the sampled dc voltages, comparing the calculated actual values of output current with the expected values in the control system, normalized diagnostic variables are established to localize single or multiple open-circuit switches. Benefit from the diagnostic variables corresponding directly to the switches of each H-bridge, this method can be easily extended to the CHBMCs with arbitrary submodules. Furthermore, the parameter estimation and enhanced detection algorithm are introduced to ensure the immunity of the diagnostic method to the large parameter changes and measurement noises. The faulty component can be accurately diagnosed within one line cycle regardless of the faulty modules and operating conditions. The effectiveness of the proposed method is substantiated using experimental results from the hardware platform of the CHBMCs.

中文翻译：

---

级联H桥多电平变换器多开关故障的快速诊断方案

级联 H 桥多电平转换器 (CHBMC) 在大功率应用中的重要性日益增加，需要更高的优先级来检测和防止故障情况。在本文中，针对 CHBMC 提出了一种当前基于残差的诊断方案，无需额外的传感器。在对采样的直流电压进行滤波、将计算出的输出电流实际值与控制系统中的预期值进行比较的前提下，建立归一化诊断变量以定位单个或多个开路开关。受益于直接对应于每个 H 桥开关的诊断变量，该方法可以轻松扩展到具有任意子模块的 CHBMC。此外，引入参数估计和增强检测算法，以确保诊断方法对大参数变化和测量噪声的免疫力。无论故障模块和运行状况如何，都可以在一个线路周期内准确诊断出故障组件。使用来自 CHBMC 硬件平台的实验结果证实了所提出方法的有效性。