混合级联多电平逆变器的改进混合调制技术

Improved hybrid modulation technique for hybrid cascade multi-level inverter

针对于Ⅲ型混合级联型多电平逆变器调制中,逆变器输出的相电压及线电压包含低频次谐波,以及大调制度下出现的超调问题,提出了一种改进的混合调制策略。该策略通过调制波和一对三角载对高压单元进行调制,得到高压单元输出的PWM波,再利用调制波与高压单元输出的PWM波的差值作为低压单元的调制波对低压单元进行调制,得到低压单元输出的PWM波。仿真与实验结果表明该策略能够消除Ⅲ逆变器输出相电压及线电压中的5次和7次低频谐波和超调现象,逆变器输出的相电压和线电压的总谐波失真(total harmonic elimination,THD)分别为14.53%和12.47%,频谱含量主要分布在2mf两侧。

Aiming at problems that output phase voltage and line voltage waveforms of III hybrid cascaded multi-level inverter including low frequency harmonics and over modulation phenomenon,an improved hybrid modulation strategy was presented. A pair of triangular carrier waveforms and modulation waveform was used to produce PWM wave of high-voltage cell,then the difference of modulation wave and PWM wave of high-voltage cell was used to produce PWM wave of low-voltage cell. Simulation and experiment results show that the total harmonic elimination（ THD） of Ⅲ hybrid cascaded multi-level inverter phase voltage and line voltage are 14. 53% and 12. 47% respectively,and harmonics distributes on both sides with 2mf.