A performance comparison study of continuous and discontinuous hybrid-PWM control for a 3-level neutral point clamped (NPC) traction inverter drive

This paper presents a performance comparison study between the proposed continuous- and discontinuous-hybrid-PWM (C-HPWM, D-HPWM) based techniques used for neutral point clamped (NPC) 3-level inverter. The H-PWM strategy uses both the advantages of carrier and space vector based PWM strategies. The duty cycles are generated using the carrier based strategy to reduce the computational complexity of the system and redundant vector states are used to keep the two DC-link capacitor voltages balanced. Detailed comparison studies are carried out in Matlab/ Simulink® and PLECS to shows the conduction and switching loss distribution with change in modulation index for IGBT and their antiparallel diodes, NPC diode with both control strategies. A 54.0 kW surface PMSM is used for this simulation studies. Moreover, the total inverter loss and torque ripples are also compared. Detailed experimental performances are also carried out with a scaled down prototype with a 6.0 kW surface PMSM, NPC inverter and real time emulator Dspace, to show the capacitor voltage deviation with both control strategies.