Sensorless Control of a Fault Tolerant Multi-level Inverter PMSM Drives in Case of an Open Circuit Fault

This paper introduces a fault tolerant multi-level inverter PMSM Drive that is capable to work in case of a single phase open circuit fault without degrading the system performance. Moreover, it can work in sensorless mode in case of an open circuit fault with the same performance as in sensor mode. The permanent magnet synchronous motor (PMSM) is fed by a 4-leg asymmetric cascaded H-Bridges multi-level inverter. The fourth leg is activated in case of an open circuit only to maintain the system performance. The reliability of the system is additionally enhanced by adopting a new method to track saliency position in case of an open circuit fault to make the system work in sensorless mode. The saliency position is obtained through measuring the dynamic current response of the healthy motor line currents due to the insulated-gate bipolar transistor (IGBT) switching actions. The new strategy includes software modifications only to the saliency tracking algorithm used in healthy mode in order to make it applicable to the reconfigured multi-level inverter in the presence of a fault. It uses only the fundamental pulse width modulation (PWM) waveform (i.e. there is no modification to the operation of the 4-leg multi-level inverter), similar to the fundamental PWM method proposed for a 3-leg multi-level inverter. Simulation results are provided to verify the effectiveness of the proposed strategy over a wide range of speeds in the case of a single-phase open circuit fault.