Unified pulse width modulated three-phase four-leg inverter based on dual-buck power cell

This paper presents a new three-phase four-leg inverter based on dual-buck power cell. Compared to traditional standard three-phase four-leg inverters with two IGBT switches in one leg, the proposed inverter incorporates dual-buck power cell, which results in several benefits. First, the dual-buck power cell allows the use of power MOSFETs for higher switching speed and efficiency improvement. Second, with the help of unique operation of dual-buck power cell, the inverter reliability is enhanced because no dead time is needed for all four legs and shoot-through concerns are totally eliminated. A unified pulse width modulation (PWM) is introduced for the proposed inverter to reduce computational burden of real-time implementation by digital signal processor (DSP). Space vector PWM (SVPWM) and discontinuous space vector PWM (DSVPWM) are analyzed under the unified PWM scheme. A prototype of the proposed inverter is designed and tested with three-phase unbalanced load under different dc bus voltage and modulation index conditions to verify the feasibility and effectiveness of the topology and the unified PWM scheme.