一种新型三电平变换器中点电压平衡调制策略  

A new neutral-point voltage balance modulation strategy for three-level converters

作　　者：张虎[1] 柴英浩 张贵 苑国锋 ZHANG Hu;CHAI Yinghao;ZHANG Gui;YUAN Guofeng(Inverter Technologies Engineering Research Center of Beijing(North China University of Technology),Beijing 100144,China)

机构地区：[1]变频技术北京市工程研究中心(北方工业大学),北京100144

出　　处：《机车电传动》2024年第2期43-50,共8页Electric Drive for Locomotives

基　　金：国家自然科学基金项目(U2368205)。

摘　　要：在大功率轨道交通装备领域中,三电平变换器因具有众多优点,在实际中得到广泛应用,但是也存在中点电压不平衡这一固有问题。为解决三电平中点箝位(NPC)型变换器存在的中点电压不平衡问题,减少输出相电流畸变情况,提高系统运行稳定性,文章提出了一种基于分析中点电荷量的双自由度新型中点电压平衡调制策略。该调制策略首先从数学分析的角度介绍了三电平变换器直流侧中点电压不平衡问题的原因;之后分析了在空间矢量脉宽调制(SVPWM)技术中,电压矢量输出序列对中点电压的影响;最后基于上述分析结果,改进传统的电压矢量输出序列,并基于改进序列的特点提出了一种新的双自由度中点电压平衡调制策略,通过双自由度的平衡因子调节作用时间。理论上,所提出的新型调制策略具有更多可控电荷量,相较于传统方法具有更良好的控制效果;仿真和试验结果验证了所提的新型调制策略对中点电压的控制效果具有更好的快速性和稳定性。综上所述,文章所提的新型双自由度调制策略可更有效解决三电平变换器存在的中点电压不平衡问题。Three-level converters have been widely used in high-power rail transit applications due to their advantages.However,they also have an inherent problem of neutral-point voltage imbalance.To address this issue in neutral point clamped(NPC)converters,reduce the output phase current distortion,and improve the system operation stability,this paper proposes a new dual degree of freedom neutral-point voltage balance modulation strategy based on the analysis of neutral-point charge.With respect to this modulation strategy,the authors first introduced the causes of the neutral-point voltage imbalance on the DC side of three-level converters from a mathematical perspective,then,analyzed the impact of voltage vector output sequences on the neutral-point voltage in space vector pulse width modulation(SVPWM),and finally improved the traditional voltage vector output sequence according to the above analysis results,and proposed a new dual degree of freedom neutral-point voltage balance modulation strategy based on the characteristics of the improved sequence.This modulation strategy adjusted the action time of balance factors with dual degree of freedom.Theoretically,the proposed new modulation strategy has more controllable charges and better control effect compared with the traditional method.The simulation and test results prove that the proposed new modulation strategy can control the neutral-point voltage faster and more stably.In summary,the proposed new modulation strategy with dual degree of freedom can effectively solve the neutral-point voltage imbalance problem in three-level converters.

关 键 词：三电平 NPC变换器 空间矢量脉宽调制 中点电压平衡 平衡因子 

分 类 号：TM46[电气工程—电器]