Unified SVPWM Algorithm and Optimization for Single-Phase Three-Level NPC Converters

The high-order harmonics caused by the modulation strategy can deteriorate power quality. The harmonic characteristics of the carrier-based pulsewidth modulation are relatively fixed and difficult to optimize, while space vector pulsewidth modulation (SVPWM) has more flexibility. The unified SVPWM design method for single-phase three-level neutral-point clamped (NPC) converters is fully presented in this article. Based on the proposed unified SVPWM method, two existing traditional vector sequences are designed first, and then several advanced multisegment SVPWM algorithms are proposed. According to the particularity of the three-level NPC topology, two hybrid SVPWM algorithms are proposed to optimize harmonic performance. Moreover, the high-order harmonic characteristics and the number of switching actions are analyzed in detail for all SVPWM algorithm modes. In addition, these SVPWM algorithms are associated and unified by introducing weight coefficients of the redundant vectors. Simulation and experimental results verify the feasibility and effectiveness of the proposed SVPWM algorithms, which show that the proposed methods can optimize high-order harmonic distribution and reduce the line current harmonics.