三电平逆变器SHEPWM多组解计算方法

Multiple Solutions for Selective Harmonic Eliminated PWM Applied to Three-Level Inverter

研究了应用于三电平NPC逆变器的特定消谐技术(Selective Harmonic Eliminated PWM,SHEPWM),针对目前文献只给出三电平SHE一组解的情况,给出了另外一组初值解经验公式,从而得到了三电平SHE的两组解。进一步研究发现在调制比较高时会存在更多组解,从而使解轨迹发生分岔现象。以开关点数N=7为例,首次给出了其在高调制比时的四组解以及开关角度随基波调制比变化的解轨迹。实际计算结果表明,利用本文所给经验公式可以快速准确得到SHE方程组的解。最后通过实验验证了文中所给四组解的正确性,并分析和比较了其谐波特性的差异,为实际应用中解的优化选择提供了依据。

This paper studies SHEPWM that is applied to three-level neutral-point-clamped inverter. Though there is only one group of solutions for three-level SHE in published papers, this paper gives another group of initial values for the solution of SHE non-linear equations, thus two groups of solutions are obtained. Further studies show that when modulation index is high there may be multiple groups of solutions. Four groups of solutions and the corresponding solution tracks are firstly given in this paper for high modulation index when switching points equals 7. Practical computation verifies the effectiveness of the formula of initial values presented in this paper. Experimental results prove that the four groups of solutions are correct and there exist differences among them in harmonic characteristic, which provides more choices in practical use.