Fault Tolerant Control Methods for Three-Level Boost T-Type Inverter

This article presents control techniques for three-level boost T-type inverter (TLB-(TI)-I-2) to address open-circuit faults (OCFs) and short-circuit faults (SCFs) of semiconductor devices. Three main groups of semiconductor failures of TLB-(TI)-I-2 are OCFs of boost switches (F1), OCFs of inverter half bridge switches (F2), and OCFs of bidirectional switches (F3). Under the proposed approaches, the inverter generates a two-level output voltage with the F1 and F2 faults, while it still generates a three-level output voltage with the F3 fault. These control techniques are extended to solve OCF and SCF of diodes, SCF of boost switches, and OCF of capacitors. Operating modes of the inverter in both normal and fault conditions are presented. Design guidelines, power loss contribution, and comparison study are included. The experimental results based on a 1-kVA prototype are carried out to verify the accuracy of the proposed methods. The result shows that the proposed methods can reduce component voltage ratings when compared to the conventional methods. In particular, the voltage rating of the inverter half-bridge switch in the F2 fault-tolerant method is reduced by at least 50% compared to the traditional techniques.