Three-Phase Switched-Capacitor Common-Grounded Multilevel Inverter for EV Application

This study aims to enhance the performance of induction motor (IM) drives by implementing a three-phase switched-capacitor Common-Grounded multilevel inverter (TCGMLI) for speed control. Transformerless multilevel inverters (TMIs) are increasingly preferred for electric vehicle applications due to their superior output quality and step-up capabilities without the need for transformers. However, existing TMIs often necessitate additional components to achieve high step-up outputs. To overcome this limitation, a seven-level (7L) switched capacitor (SC) TMI with a common-ground feature. This design incorporates a soft-charging resonant cell to minimize inrush current. Achieving low total harmonic distortion (THD) and precise speed regulation of the induction motor is facilitated by maintaining a constant (V/f) ratio and managing slip speed. A proportional-integral (PI) controller is employed to stabilize the motor speed. The closed-loop system's performance is evaluated under various scenarios, including changes in reference speed, dynamic loads, and speed disturbances. The paper presents a comparative analysis of the performance and efficiency o f an IM drive using v/f control versus a closed-loop TSCMLI system. Simulation results, obtained using MATLAB/SIMULINK, validate the effectiveness of the proposed system in improving motor drive performance and efficiency.