一种三电平中点钳位变流器改进型载波反相层叠脉宽调制策略

Improved Phase Opposition Disposition Pulse Width Modulation Strategy for Three-Level Neutral Point Clamped Converter

三电平中点钳位变流器载波反相层叠脉宽调制(PODPWM)策略可降低共模电压,但其存在相电压两电平跳变(TLJ)和难以添加中点电位平衡控制策略的缺陷。为解决以上缺陷,该文首先分析PODPWM的基本原理及其等效的空间矢量序列。在此基础上,通过对调制波叠加特定零序分量并在调制波采样值过零点处选择使用特定方向的三角载波,得到可防止TLJ的改进型PODPWM(IPODPWM)及其中点电位平衡控制策略。最后推导IPODPWM作用下的共模电压、直流电压利用率、相电压频谱和开关频率,并设计基于IPODPWM的同步调制方法。仿真和实验结果表明,所提IPODPWM能够避免相电压两电平跳变并控制中点电位平衡,且具有共模电压小、直流电压利用率高的优点。

The phase opposition disposition PWM(PODPWM)strategy of three-level neutral point clamped converter can reduce the common-mode voltage,but it has the defects of two-level jump(TLJ)and is difficult to design the neutral point voltage balance control strategy.Therefore,this paper first analyzes the basic principle of PODPWM and its equivalent space vector sequence.Accordingly,an improved PODPWM(IPODPWM)and its neutral point voltage balance control strategy for preventing TLJ are obtained by selecting the triangular carrier in a specific direction at the zero crossing point of the modulation wave and superimposing a specific zero sequence component on the modulation wave.Finally,the common mode voltage,DC voltage utilization,phase voltage spectrum and switching frequency under IPODPWM are derived,and a synchronized modulation method based on IPODPWM is designed.Simulation and experimental results show that the IPODPWM proposed in this paper can avoid the two-level jump of phase voltage and control the neutral point voltage balance,and has the advantages of small common-mode voltage and high DC voltage utilization.