Three‐level saddle space vector pulse width modulation strategy based on two‐level space vector pulse width modulation for neutral‐point‐clamped three‐level inverters

Abstract

This study proposes a three-level saddle space vector pulse width modulation (SVPWM) strategy based on two-level SVPWM (TBT_SAPWM) for neutral-point-clamped (NPC) three-level inverters. According to the analysis of the conventional three-level SVPWM strategy based on two-level SVPWM (CTBT_SVPWM) and the proposed TBT_SAPWM strategy, the modulation wave expressions of the two strategies are derived. Compared to the CTBT_SVPWM strategy, each main sector has its own independent area, and determining the main sectors or regions becomes easier with the proposed TBT_SAPWM strategy. Moreover, by optimising the switching states, the proposed TBT_SAPWM strategy makes on-state duration of one selected phase equal to that of the other selected phases in a switching cycle. Therefore, the three-phase modulation waves are saddle waves at the full range of fundamental wave modulation ratios. According to the experimental results in this study, the proposed TBT_SAPWM strategy has better performances in terms of the output harmonics and the neutral-point voltage ripple, compared to the CTBT_SVPWM strategy. The feasibility and effectiveness of the proposed strategy are verified by the experimental platform of an NPC three-level inverter based on the digital signal processor and complex programmable logic device.