Fault‐Tolerant Control of NPC Three‐Level PWM Rectifier Under Switch Open‐Circuit Faults

In modern power systems, the fault risk of existing three‐level PWM rectifiers is on the rise, posing a threat to system safety. This paper proposes a fault‐tolerant control strategy suitable for NPC three‐level PWM rectifiers, and in this paper, the open‐circuit fault mainly refers to gate‐drive signal loss induced switching open‐circuit conditions, while the antiparallel diodes are assumed to remain operational. Firstly, a fast and accurate single‐switch fault diagnosis method for switch open‐circuit faults is constructed based on changes in current paths. Subsequently, faults are classified into three categories according to their impacts on switching states and space vectors, and compensation‐based fault tolerance is achieved using voltage space vector redundancy technology and modified PWM switching patterns, respectively. Simulations and controller‐in‐the‐loop (CIL) experiments verify that the strategy effectively suppresses grid current distortion and DC‐side voltage fluctuations after faults, reducing the total harmonic distortion (THD) significantly for Type I/II faults and stabilising the DC‐link voltage within 0.07 s for Type III faults. It ensures the stable operation of the rectifier under fault conditions and provides technical support for improving the reliability of high‐power grid‐connected systems.