A model predictive control based fault-tolerant control strategy for T-type three-level inverters

摘要

Nowadays, research on the reliability improvement of T-type three-level inverters is studied as an important issue. In this paper, a novel fault tolerant control strategy based on model predictive control (MPC) is proposed for open-circuit faults in switch devices. When an open-circuit fault occurs to neutral-point switches, the impossible switching states of zero- and small-voltage vectors should be replaced by the redundancy switching states. In addition, to avoid the use of the impossible medium-voltage vectors, the weight coefficient should be set to infinity. In case of the open-circuit fault in half-bridge switches, the large-voltage vectors become impossible. In order to avoid the distortion of the output, only the possible zero and small voltage vectors are used to track the reference current. Furthermore, in order to guarantee the balance of neutral-point (NP) voltage for the 3LT²I, the weight coefficient of the small- and medium-voltage vectors which can influence the NP potential is properly modified. Simulation and experimental results are provided to verify the validity and feasibility of the proposed strategy.