一种三电平三相四桥臂逆变器中点电位平衡策略

A Novel Strategy of Neutral Point Potential Balancing for Three-Level Three-Phase Four-leg Inverters

针对三电平三相四桥臂逆变器数学模型复杂和不对称运行时易导致直流电容中点电位漂移的弊端,本文采用降维策略,将三维数学模型降为平面模型和一维模型的简单叠加;基于空间矢量脉宽调制(SVPWM),分析各种矢量对中点电位的影响,通过合理选择和优化开关矢量,使单个采样周期内流过直流电容中点的平均电流严格为零,从而有效抑制了中点电位的漂移。仿真和实验结果表明了本文所提算法在宽范围调制比和不对称负载条件下均能有效保证直流侧中点电位的平衡。

Aimed at the drawbacks of complicated three-dimensional model and neutral point potential drifting in three-level three-phase four-leg inverters, a novel strategy is proposed in this paper. It keeps neutral point potential balanced by descending dimension, analyzes the influence of each switching states on the neutral point potential, and optimizes switching states based on space vector modulation. The average current flowing through the neutral point of DC capacitors is absolutely zero during each sampling period, and hence the neutral point potential is balanced effectively. The simulation and experimental results verify that the proposed strategy can eliminate the neutral point potential drifting with modulation ratio and load conditions over a big range.