A Decentralized Fault-Tolerant Control Strategy for Multilevel CHB Inverters Based on a Multiband Hysteresis Modulation

In recent decades, multilevel inverters have become increasingly common in medium-voltage applications. Among the various topologies, the cascaded H-bridge (CHB) stands out as a particularly fault-tolerant configuration. Its modular structure, composed of multiple H-bridge inverters connected in series, allows for the implementation of a decentralized control strategy in which every H-bridge module is considered to act autonomously. In this paper, such decentralized control is described for the current control loop based on a multiband hysteresis controller, aiming at increasing the flexibility of the system and guaranteeing the fault-tolerant operation while inherently balancing the states of charge (SoC) of the power sources without further communication. Simulations have been carried out to validate the proposed method and identify its limitations. A hardware implementation is used to demonstrate the load balancing between the modules under non-ideal conditions.