A new fault tolerant SVPWM strategy for multilevel converters

Fault tolerant and survivable operation schemes for multi-level converters, that interface the grid and critical loads, have been gathering attention for enhanced reliability. In case short-circuit or open-circuit faults occur in one or multiple voltage cells, the space vector pulse width modulation (SVPWM) control algorithm has to be modified according to the available voltage vectors for survivable operation. This paper proposes a new fault tolerant SVPWM strategy based on offset vector insertion, which allows controlling the multilevel converter as a two-level converter. A robust offset vector locating algorithm, which finds the feasible offset vector in case of short-circuit and open-circuit conditions, is presented. A single voltage cell short circuit fault is demonstrated on a seven-level hybrid input-switched multi-level converter to prove the effectiveness of the proposed survivable scheme.