Three-Phase ZVS-TNPC Inverter With Common-Mode Voltage Suppression

In response to the issues of multi-auxiliary components and low device utilization, as well as high common-mode voltage (CMV) in the current three-phase three-level neutral-point-clamped soft-switching inverters, this article proposed a novel high-integrated three-phase zero-voltage soft-switching T-type neutral-point-clamped inverter (ZVS-TNPC). This inverter utilized the “function multiplexing” of auxiliary devices to reduce the number of auxiliary components. At the same time, to avoid the interphase commutation coupling issues that may arise from the sharing of auxiliary components and to reduce the fluctuation of CMV, a specific five-segment medium vector pulsewidth modulation strategy was designed. This strategy ensured that the two vertical switching devices that switch simultaneously came from different phases’ positive and negative polarity bridge arms, creating conditions that were necessary for soft switching. The modulation strategy leveraged the principle of opposite trends in the impact of differential-mode voltage characteristics between the same type of soft-switching commutations but with different polarities, thereby suppressing the CMV amplitude of the three-phase ZVS-TNPC over the entire line frequency cycle to below U_dc/6. Compared to other NPC soft-switching schemes, the proposed three-phase ZVS-TNPC could achieve soft-switching of all high-frequency switching devices and suppress CMV. Finally, a 5.6 kW/100 kHz TNPC prototype inverter was built to verify the advantages of the proposed circuit in terms of efficiency and CMV characteristics.