A Reconfigurable Four-Level/Six-Level Inverter-Fed Variable Pole�Phase Induction Motor Drive With Fault Tolerant Capability

Abstract

This article presents a fault-tolerant multilevel inverter configuration for a nine-phase variable pole-phase induction motor (VPIM) drive, mainly targeted for electric vehicle applications where efficiency, low-torque ripple, and reliable operation are essential. The traditional VPIM drives suffer lesser efficiency, lower fault-handling capability, complex inverter circuits, high-torque ripple, and poor DC bus utilization. To overcome these issues, a new inverter structure is developed by integrating three-leg and four-leg inverter modules, where each leg consists of two switches. This configuration can generate four levels in 4pole-9phase (4po-9ph) mode and six levels in 12pole-3phase (12po-3ph) mode. This improvement in voltage levels significantly reduces voltage total harmonic distortion (THD) and current ripple, resulting in better torque ripple profile and system efficiency. The fourth leg of an inverter plays an important role in enabling the changeover of pole phase modes and suppressing circulating currents, particularly when space-vector PWM (SVPWM) is used. A detailed mathematical analysis of phase voltage is presented to explain the reduction in current and torque ripple. Further, the performance of the VPIM drive is evaluated under different torque conditions using ANSYS Maxwell simulations. A comparative analysis of VPIM drive performance is conducted for different voltage level configurations in terms of torque ripple, DC bus voltage utilization, voltage THD, efficiency, power factor, losses, etc. The experimental validation on a 5-hp prototype confirms the effectiveness of the proposed inverter under both normal and fault conditions. � 1982-2012 IEEE.