Fault-Tolerant Control and Its Transit Process for Three-Level NPC Inverter Fed Induction Motor System

The three-level neutral-point-clamped (3LNPC) inverters require more reliable control strategies due to the increasing demand for safe operation on a critical occasion. In this digest, a fault-tolerant strategy and its transit process are presented for the induction motor (IM) system fed by the 3LNPC inverters. The mixed logic dynamic model (MLD) is used to generate the three-phase stator current residuals. Then, the residual information is used to identify the fault leg. Based on the detection results, a fault-tolerant control strategy, which is achieved by reconfiguring the topology and changing the modulation strategy, is introduced to ensure continuous and stable operation. Moreover, the transition from fault detection to tolerant control process is analyzed for improving the control performance of the system. The results have verified that the detection time, unbalanced dc-link capacitor voltage, and system operation conditions have an effect on the system operation performance. The feasibility and effectiveness of the proposed control strategy are verified by simulation.