Switching-Leg Redundancy in Power-Electronic Converters: Topologies, Strategies, and Emerging Directions

Switching-leg redundancy has become a key design philosophy for modern power-electronic converters, boosting reliability, fault resilience and uninterrupted service. This survey consolidates recent advances in redundant-leg concepts across multi-level inverters, modular multilevel converters (MMCs) and power-electronic building blocks (PEBBs). Redundancy schemes are reviewed from device to full-converter scale, alongside fault-detection, diagnostic and reliability-assessment methods, plus adaptive-control techniques. Results show leg-level redundancy offers the best cost-to-performance compromise relative to device- or module-level options. Contemporary fault-tolerant multi-level inverter configurations markedly raise system dependability; several render a converter immune to both single- and multi-switch faults. AI-driven diagnostics routinely exceed 95% accuracy under varied conditions. The review also highlights self-healing power architectures and reconfigurable topologies that autonomously restore operation with no human input