A New Control Method to Operate Isolated MLI as a Fast Fault-Tolerant Configuration for Handling a Wide Variety of Open Circuit Failures

This article describes the design of a fully fault-tolerant inverter configuration specifically for grid-connected and constant speed drive applications. The approach focuses on maintaining fault tolerance without increasing the device count in existing isolated configurations. The proposed topology employs a common cell and standard cells, each divided into operational and redundant half-bridge legs. Under normal operating conditions, the output voltage generates from operational legs. But, in the event of a switch fault, the corresponding switch in the redundant leg activates and replacing the fault switch. Besides, the proposed fault-tolerant control scheme operates within a single fundamental cycle of the output voltage waveform. During this cycle, each switch undergoes four rounds of scrutiny before any isolation occurs which significantly reducing the chances of misidentifying faults or triggering gate misfires. The fault detection and response are managed using only two output sensors (one for voltage and one for current), which streamlines the system and enhances its efficiency. The article includes a comparative study that demonstrates the effectiveness and practicality of this fault-tolerant approach compared to similar topologies and techniques. The proposed fault-tolerant topology and method will be validated through MATLAB Simulink simulations and confirmed with a hardware prototype.