基于零序电压范围扩展增强三电平逆变器七段RCMV-PWM中点电位平衡能力

In the existing three-level carrier-based pulse width modulation (CBPWM) methods, variations in carrier waveforms and the requirements for common-mode voltage (CMV) reduction inherently constrain the range of injected zero-sequence voltage (ZSV), thereby degrading neutral point (NP) potential control performance. This article studies the NP potential balance capability enhancing method based on ZSV expansion for seven-segment reduced CMV PWM (RCMV-PWM). The range of ZSV with various distribution of carrier waves is theoretically analyzed and the carrier waveforms are adapted to obtain the maximal ZSV range considering the constrains of limiting the CMV amplitude with sixth of the dc-link voltage. The optimal ZSV calculation method within the derived maximal range is given in detail. This approach effectively reduces NP potential fluctuations in low modulation indexes and low power factors. Finally, experimental results demonstrate the effectiveness of the proposed method.