A Fault-Tolerant Control for Hybrid Active Neutral-Point-Clamped Converters With Shared Redundant Unit Under Multiswitch Open-Circuit Fault

Hybrid active neutral-point-clamped (HANPC) converters comprising silicon and silicon carbide devices are promising topologies in middle-low power conversion systems. The reliable operation of such converters is highly desirable, which depends on effective fault-tolerant schemes. However, existing schemes do not provide HANPC converters with the ability to tolerate the failures of multiple outer-switches with satisfactory fault-tolerant performance in terms of neutral-point voltage balancing and rated output voltage. To address this issue, the shared redundant unit is configured into HANPC converters. The matched fault-tolerant control strategy is proposed with rearranged switching sequences by utilizing the available space vector. In this context, the feasible region of the designed vector sequence (FRDVS) for fault-tolerant operation of HANPC converters is defined. Subsequently, the boundaries of FRDVS are quantitatively analyzed under different power factors. The improved fault-tolerant scheme allows the continuous operation of HANPC converters at rated capacity during the fault period, even up to open-circuit faults at all outer-switches. Experimental results are presented to verify the effectiveness of the proposed fault-tolerant scheme.