A Multilevel Inverter With a Single Battery Source and a High-Frequency Link for Electric Vehicles

Multilevel inverter topologies with cascaded H-bridges fed by asymmetrical direct-current (DC) voltage sources have higher output voltage levels than symmetrical ones and are preferred in electric vehicles (EVs). However, these converters are difficult to incorporate in electric vehicles because the system requires a significant number of isolated DC supplies. This study presents a novel multilevel inverter drive topology, which is powered by a single battery source and uses a small, affordable high-frequency link (HFL) to generate isolated DC sources across H-bridges. The HFL consists of a Single-Input Multiple-Output (SIMO) flyback converter and a Bidirectional DC-DC (BDC) converter, which enables dynamic voltage control with a finite number of levels. This study focuses on a 27-level inverter fed induction motor drive with a cross-regulated DC link. In addition, the proposed multilevel drive system enables a smooth transition from motoring to regenerative charging of the battery with three-level rectifier operation of the cascaded H-bridge converter. The hybrid nearest level control (HNLC) modulation scheme is deployed in the proposed drive to control the inverter voltage over a wide range of speed variations without compromising the number of voltage levels. The proposed topology was simulated using MATLAB/Simulink and validated using hardware experiments.