This paper presents an extensive comparative study between a two- and three-level inverter for electric vehicle traction applications. An advanced control strategy for balancing the two dc-link capacitors is also proposed. In this paper, the main focus is on the total voltage harmonic distortion (%THDv), the analytical derivation of the three-level capacitor currents, and the voltage balancing of two capacitor voltages. For generating the gate signals, space vector pulse width modulation (SV-PWM) is used. The developed voltage-balancing scheme helps to reduce the number of converter switching sequences, compared with the conventional SV-PWM strategy, and keeps the voltage difference between the two dc-link capacitors at the desired voltage level. The developed test-bench is used for a permanent magnet synchronous machine drive for electric vehicle (EV) applications. Detailed simulation studies are performed using MATLAB/Simulink block set and experimental verification is achieved using dSpace based real-time simulator. Both the simulation and experimental results show a significant improvement in reduction of total harmonic distortion (%THDv) for the three-level inverter.
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Choudhury et al. (2014) studied this question.