A multi-mode fault-tolerant control strategy for cascaded Hbridge multilevel inverters
Résumé
This paper proposes a new fault-tolerant control (FTC) strategy, for cascaded H-bridge multilevel inverters, totolerate single or double arbitrary Insulated Gate Bipolar Transistor (IGBT) faults. Initially, all faulty modes are classified intothree fault clusters according to the number and location of faulty IGBTs. Then, the matching mechanism of the multi-modeFTC strategy corresponding to the three clusters is described, and the appropriate FTC algorithm is selected for each cluster.A new FTC method is proposed for Cluster I including double IGBTs faults in different H-bridges and different groups, whichimproves the utilization efficiency of healthy IGBTs in the faulty H-bridges, and minimizes the voltage level drop after thefault. Finally, the multi-mode FTC strategy has been applied to a 7-level inverter through simulation. Results have shownsignificant improvement of the output voltage waveform symmetry and harmonic distortion for the three clusters. The newFTC method has been applied to an experimental 5-level inverter. The obtained results confirm the validity of themethodology. With the proposed strategy, the output voltage waveform has recovered its symmetry, eliminated theundesirable DC component and achieved lower harmonic distortions.