DC infeed fault ride-through operation of cascaded H-bridge multilevel inverter based on DC-coupled thyristors

• DC infeed fault ride-through strategy for CHB-X systems is proposed. • Thyristor-based coupling enables autonomous DC-link voltage balancing. • Sensor and DC/DC converter faults are tolerated without extra hardware. • Adaptive switching achieves rapid voltage recovery under fault conditions. • Validated on 2 kW prototype with experimental fault scenario tests. The cascaded H-bridge multilevel inverter (CHB) presents a promising solution for utility-scale renewable energy integration, offering superior modularity, distributed MPPT capability, and direct high-voltage interfacing. However, its reliability remains challenging due to component-intensive architecture involving multiple DC sources, switching devices, and monitoring circuits. This paper proposes a novel fault-tolerant strategy to address critical failure modes in both power conversion and sensing circuits, which typically cause current/voltage tracking errors, power mismatches, DC-link voltage imbalances, and system instability. The developed approach employs innovative DC-coupling thyristor configurations combined with adaptive switching algorithms to achieve autonomous voltage self-balancing during fault conditions. By strategically activating adjacent DC-link couplings through optimized switching sequences, the system enables rapid fault current redistribution and voltage rebalancing without requiring additional balancing circuits. The proposed DC-coupled thyristor-based DC-feed ride-through improves system reliability by 13%, with the reliability index rising from 0.866 to 0.981. Experimental results from a 2 kW/260 V setup are presented to verify that the proposed method has excellent cell-fault tolerance, enabling rapid recovery of DC voltages at all failure points.