Diagnosis and Fault-Tolerant Control of Three-Phase AC–DC PWM Converter Systems

There is the possibility of an open-switch fault in a three-phase ac-dc pulsewidth-modulation (PWM) converter due to problems with the switching devices. In this case, the converter causes unbalanced input ac currents including increased harmonics and dc-link voltage ripples. In this paper, the one-open-switch fault case of six switching elements is analyzed by considering the switching patterns of space vector PWM and the directions of a faulty phase current to prove the cases of the fault. In addition, this paper proposes a detection method for open-switch faults and a fault-tolerant control method to minimize the imbalance of the input ac currents and the voltage ripple of the dc link in a three-phase ac-dc PWM converter. The usefulness of this paper is verified through experimental results.