Redundant Switch and Triac-Based Fault-Tolerant Multilevel Inverter for Uninterruptible Power Supply Applications

Recently, multilevel inverters (MLIs) have been extensively used in different renewable energy systems due to various reasons, including enhanced efficiency, improved power handling capability, improved output quality, etc. However, as the number of switching devices increases to achieve multilevel voltage output, ensuring the reliability of these converters present a growing challenge. Hence, this paper proposes a novel fault-tolerant multilevel inverter that offers resilience against various switch faults and can operate in both symmetric and asymmetric voltage modes. The proposed topology can achieve fault tolerance by incorporating a redundant unit consisting of switches and triacs to maintain rated power. Additionally, a new parameter is introduced to evaluate the fault-tolerant capabilities of converter topologies, providing deeper insights into their reliability. Experimental validation of the proposed converter is conducted on a 500 W prototype to validate the robustness of the presented MLI under diverse fault conditions. Further, comparative analysis has been demonstrated to underscore the advantages of the proposed topology, highlighting its superior performance across multiple metrics such as fault-tolerant efficacy, reliability, and efficiency. Furthermore, the generalized structure of the proposed fault-tolerant MLI is presented to emphasize its versatility and scalability.