Indirect Field-Oriented Control of an Induction Machine Fed by an Advanced Multilevel Converter for Electric-Vehicle Applications: A Comparative Analysis with a Cascaded Structure

This paper presents a rigorous comparison of two three-phase, five-level inverters intended to supply a squirrel-cage induction machine. Such reduced-component multilevel structures are of particular interest for electric-vehicle traction drives, where a lower switch and gate-driver count directly benefits converter cost, volume, and reliability. The first structure, adopted as the reference, is a cascaded H-bridge inverter comprising two cells per phase, i.e., twenty-four controlled switches and six isolated DC sources. The second combines a classical H-bridge with an auxiliary level-selection cell and requires only fifteen controlled switches together with twelve diodes for the three legs as a whole. Both converters are coupled to the same machine and subjected to an indirect field-oriented control scheme aligned with the rotor flux, a level-shifted carrier PWM, identical regulators, and identical test scenarios. Topology is thus the sole variable under study. The structural analysis shows that configuration B reduces the number of controlled switches, and hence of gate-drive channels, by 37.5%. Its effect on the device count depends on the counting convention: discrete semiconductors increase from 24 to 27 (+12.5%), whereas semiconductor dies decrease from 48 to 42 (−12.5%), because the cascaded H-bridge (CHB) inverter already integrates 24 antiparallel diodes. Configuration B also raises the total blocking voltage by 12.5% and doubles the blocking voltage of four switches per phase; these devices remain within the same voltage class at the DC-link voltage studied, but would require a higher class at traction ratings. With three isolated DC sources, as in the simulated configurations, the cost indices of configuration B are 1–3% higher than those of the CHB, so that its net structural benefit reduces to the saving in gate-drive channels. A further reduction in isolated DC sources is possible only with a shared-bus variant, which is analyzed structurally but not simulated.