Fault-Tolerant and Reconfiguration Control for Boost Multi-level NPC Converter Fed Doubly Fed Induction Machines

Double fed induction machine (DFIM) is preferred in various industrial applications, as it provides variable speed operation with reduced power converter rating and high dynamic stability. On rotor side, back-to-back voltage source converter (VSC) is act as excitation system and controls real and reactive power of the machine. Boost multi-level neutral point clamped (NPC) VSC is emerging in industrial applications due to the high dc link voltage utilization and less current THD. Full power converter redundancy in large rated VSC fed DFIM is challengeable and it is not yet employed in any practical applications such wind power generation and pumped-hydro power units. Therefore, fault-tolerant control (FTC) of VSC is mandatory for the continuous operation of unit by the project authorities of the units. This paper presents the fault tolerant and reconfiguration control approach for a boost NPC converter fed DFIM unit at open circuit faults in all controlled switches/devices. FTC during open-switch faults are investigated with the help of converter output voltage. Fault detection and isolation is achieved through the rotor currents and dc link voltage. A 2 MW DFIM is simulated in Matlab/Simulink environment to verify the operation of the proposed fault tolerant control.