Opposite Vector Based Phase Shift Carrier Space Vector Pulse Width Modulation for Extending the Voltage Balance Region in Single-Phase 3LNPC Cascaded Rectifier

A phase shift carrier space vector pulse width modulation scheme based on an opposite vector voltage balancing strategy is proposed to extend the balance region of dc-link capacitor voltages for a single-phase three-level neutral point clamped cascaded rectifier (3LNPC-CR). The internal-module and mutual-module 3LNPC-CR balancing strategies are simultaneously applied to improve the voltage balancing capacity when the dc loads are unbalanced. The voltage balance boundaries of three space vector pulse width modulations using the traditional strategy, the zero vector strategy, and the opposite vector strategy are compared. The analysis results indicate that the proposed modulation algorithm maintained balanced voltages for all modules even if one load of the module was removed. Meanwhile, the equalization of the neutral point voltage for the single-phase 3LNPC-CR was also achieved. Finally, the voltage balancing capacity and rectifier performance of the proposed strategy was verified by simulations and experiments.