Five-Level Three-Phase H-Bridge Inverter with Transformerless Isolated DC Sources for an Induction Motor Drive

The H-bridge is a promising multilevel inverter with a modular structure that facilitates maintenance. However, modular multilevel inverters generally require more isolated DC sources, complicating the battery management system in battery-based electric vehicles. This article proposes an isolated DC source method without a transformer by utilizing the charging and discharging intervals of the DC-link capacitor. This method enables the inverter to operate with only one battery pack, addressing the issue of DC source imbalance in modular inverters without the need for extra control systems and sensors. Simulation results show that the inverter can generate a five-level three-phase waveform to drive the induction motor, reaching steady-state speeds of 1490.74 to 1490.94 rpm with a stable torque ripple of 75.88 to 165.66 Nm. This demonstrates that the proposed configuration can be effectively utilized in traction systems.