Fault Detection and Localization for Cascaded H-Bridge Multilevel Converter with Model Predictive Control

The cascaded H-bridge (CHB) multilevel converter has been used in various applications, such as the STATCOMs and solid-state transformers. Due to its modular structure, fault tolerance can be incorporated in the CHB multilevel converter. In this article, a model predictive control (MPC)-based fault detection and localization (FDL) scheme is proposed for the CHB multilevel converter that utilizes the already-installed ac current measurement and does not require additional sensors. The proposed FDL scheme can detect single or multiple open-circuit switch faults in the CHB multilevel converter by comparing the predicted states of the MPC controller with the actual measured states. The detected fault(s) is(are) further localized through a fault localization matrix which narrows down the faulty switch using historical fault data. The proposed scheme is shown to complete the FDL process for both single or multiple open-switch faults within a fundamental cycle period, even during low-load conditions. It has also been shown that the proposed scheme is immune to system dynamics such as load and voltage variations, and has been validated experimentally for various open-circuit fault scenarios.