Survey of Open-circuit Fault Detection and Localization Methods Applicable to Cascaded H-bridge Multilevel Converters

Cascaded H-bridge (CHB) multilevel converter is widely used for medium voltage motor drives, Static Synchronous Compensator (STATCOMs) and solid-state transformers because of its advantages such as modular design, low harmonic distortion of input current and lower grid-side filter requirements compared to two-level converters. Among the failures in active devices, detection and localization of open-circuit (OC) faults either due to bond-wire lift off (device-side failures) or malfunction of gate driver (drive-side failures) are extensively studied. In this paper, fault detection and localization methods proposed in literature for CHB multilevel converters are analyzed and compared with respect to the time taken for fault localization and additional sensor requirements. For ease of understanding, the methods are classified as model-based, feature-based and hardware-based, and suitability of each classification is recommended for different applications.