单相五电平逆变器的多载波PWM方法分析

Analysis of multi-carrier PWM methods for single-phasefive-level inverter

针对单相五电平级联逆变器,对不同的多载波PWM方法进行分析。采用载波移相(PS)PWM方式时,其输出波形中含有幅值较大的高次谐波,而载波垂直分布(CD)PWM方式不存在这些问题,但是CDPWM调制方式的低次谐波比较大。与CDPWM调制方式相比,采用PSPWM调制方式所产生的低次谐波分量非常小。结合2种PWM调制方式各自的优点,提出一种混合多载波PWM方法。通过对典型的五电平PWM单相逆变电路的Matlab仿真计算,证明了混合多载波PWM法输出波形中的高次谐波含量小,低次谐波分量介于PSPWM调制方式和CDPWM调制方式之间,总的谐波畸变率最小。因此,对于单相的五电平逆变器而言,混合调制方式为最优。

Different multi- carrier PWM methods for single- phase five- level cascaded inverter are analyzed. The high order harmonics have bigger amplitude in its output when PSPWM method is adopted while the low order harmonics have bigger amplitude when CDPWM method is adopted. A hybrid PWM method combining PSPWM and CDPWM is presented. The simulative calculation with Matlab for typical single-phase five-level inverter circuit shows that,the high order harmonics in the output of hybrid PWM method are less and its low order harmonics are between PSPWM and CDPWM,and its total harmonic distortion is the least. For single-phase five-level inverter,the proposed hybrid PWM method is the best.