An Analytical Simplified Algorithm With Unified Zero-Sequence Component Injection for 3L Symmetrical DPWM

Among the existing discontinuous pulsewidth modulation (DPWM) schemes for three-level converters, the symmetrical DPWM can achieve relatively low common-mode voltages, and the redundant vectors are overall distributed equally for balancing the neutral point voltage. However, there is still lack of simple and unified analytical expressions for the zero-sequence component, which can be injected into modulation waves for implementing the symmetrical DPWM. In this letter, to further simplify the implementation of the symmetrical DPWM, a comprehensible derivation process for calculating the zero-sequence component is presented from the perspective of vector synthesis. The dwell times of redundant vectors are intuitively presented and redistributed, and a unified zero-sequence component is analytically derived. Only seven simple equations are required for calculating final modulation waves with the unified zero-sequence component injection, presenting a significantly reduced computation burden.