<p>Modular Multilevel Converters (MMCs) have emerged as prominent solutions for high-voltage and high-power applications due to their scalability, modularity, and superior performance. However, MMCs are susceptible to different types of faults, including open circuit faults that occur in submodules. Various methods to diagnose these faults have been proposed; however, very few studies have considered open circuit faults where both the IGBT and the diode are damaged. In this article, an intelligent fault detection and localization algorithm based on fuzzy logic and the discrete wavelet transform (DWT) is presented to address this type of open circuit fault in the submodule of the modular multilevel converter (MMC). First, the discrete wavelet transform (DWT) is used to decompose the measured capacitor voltage signals and extract their detail coefficients. Then, the root mean square (RMS) of these coefficients is computed. Finally, these quantities, along with the original capacitor voltage signals, are used as input data for the fuzzy logic algorithm to distinguish between similar fault signatures. Simulation results confirm that the suggested algorithm can accurately and rapidly detect and locate this type of open circuit faults, demonstrating the effectiveness and reliability of the proposed method.</p>