Open-Switch Fault-Tolerant Scheme for Four-Level $\pi$-Type Inverter Fed Propulsion Drive for Marine Transportation

The reliability of propulsion drives is a critical aspect of any electrified marine propulsion system. Utilizing a multilevel inverter in these applications improves both power quality and reliability owing to the presence of redundant levels. This article proposes an open-switch fault-tolerant scheme for a four-level <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\pi$</tex>-type inverter. Open switch faults in both the halfbridge (HB) switches and the neutral point (NP) switches are analyzed based on switching states. In accordance with that four-level inverter is further divided into sub-inverters. During open-switch fault condition, healthy sub-inverters are operated by proposed modified carrier-based pulse-width modulation (PWM) technique. The operation of healthy sub-inverters enables the uninterrupted operation of the marine propulsion drives. To analyze and validate the effectiveness of the proposed PWM scheme, a simulation study has been conducted using MATLAB/Simulink tool.