Fault-Tolerant Strategy for the MMC-Based PV System With Faults Detection and Converter Reconfiguration Using Permutation Algorithms

The modular multilevel converter has gained popularity in various applications, including photovoltaic (PV) solar energy conversion. Its modular structure allows for the transformation of an MMC into an MMC-based photovoltaic system, sharing key operational characteristics such as modularity, flexibility, redundancy, increased efficiency, and fault tolerance. To ensure the reliability and uninterrupted operation of the modified MMC, even in the event of potential failures in the photovoltaic submodules (PVSMs), a fault-tolerant strategy is developed in this study. It assumes that the Maximum Power Point Tracking (MPPT) of the PVSMs is already guaranteed. Redundant submodules (rSM) are utilized to maintain power balance between the converter arms through voltage control, while reserve submodules (RSMs) are in place to rescue the converter in case of a failure. The detection and localization of faults in the PVSMs/rSMs are achieved through sliding mode observers (SMOs), and the converter reconfiguration is carried out using the proposed permutation algorithms for switching signals and SMs voltages. For precise control of the output current and electrical grid connection, the $dq$ -reference frame control method is employed. To validate these proposed algorithms, time-domain simulations are conducted using the Simulink/Matlab software