摘要：近年来，电力电子技术的发展很迅速。在工业控制中，多电平逆变器得到了普遍应用。

多电平逆变器是一种开关频率低、开关器件电压应力小的新型逆变器,其输出波形质量高。在高电压和大功率的场所中,经常会用到多电平逆变器电路.

论文以三电平为例，简述了多电平逆变器的研究背景，介绍了三种典型的三电平逆变器主电路结构；目前国内外研究和应用的主流电路为二极管箝位型（NPC）三电平逆变器，不过在使用时候出现了很多问题，其中包括中点电位不平衡。中点电位不平衡会带来很多问题：比如，输出的电压波形畸变，使电容的寿命降低等。文章分析了中点电位不平衡的本质原因，介绍了其控制方法，即电压空间矢量调制法（SVPWM）；最后，通过仿真实验验证了本文解决方案的有效性，给出了实验波形。57878

毕业论文关键词：中点箝位型三电平逆变器，中点电位平衡，空间电压矢量调制，MATLAB仿真

Abstract：In recent years, the power electronic technology develops very quickly. Multilevel inverter has been widely applied in industrial control field.

Multilevel inverter is a new type of inverter with low switch frequency, small compressive force, and good output waveform. Multilevel inverters are applied in the high voltage and high power field. 

Three-level inverter is taken as an example, and the research background is described, then the main circuit of three-level inverter is introduced. The mainly researched and applied three-level inverter is NPC three-level inverter around the world. However the NPC three-level inverter has many problems, such as the neutral voltage imbalance, the reducing service life of capacitance and so on. The  intrinsic reason of neutral voltage unbalance is analyzed, the control strategy——SVPWM is introduced Finally, the effectiveness of the solution is verified by simulation experiments, the experimental waveforms are given.

Keywords：Neutral point clamped three level inverter，Neutral point voltage balance, Voltage space vector modulation, MATLAB simulation

目录

1  绪论 4

1.1  三电平逆变器的背景 4

1.2  三种典范电路的拓扑及优缺点 4

1.2.1  二极管箝位型三电平逆变器拓扑 4

1.2.2  悬浮电容三电平逆变器拓扑 5

1.2.3  级联型多电平逆变器拓扑 5

1.3  二极管箝位型三电平逆变器(NPC) 6

2  三电平逆变器空间电压矢量调制（SVPWM）方式 8

2.1  三电平空间电压矢量图、划分扇区区域 9

2.2  参考电压矢量位置确定输出电压矢量 11

2.3  输出电压矢量的作用时间 12

2.4  开关矢量优化选择 14

3  三电平逆变器中点电位平衡的分析 18

3.1  各种可能导致电位波动与不平衡的因素 18

3.2  三电平逆变器中点电压波动机理的分析 19

3.2.1  电压矢量对中点电位的影响 19

3.2.2  中性点的电流分析 20

3.3  波动与不平衡的区别