多电平变流器多载波PWM技术的研究

Research on multi-carrier PWM technique for multi-level converters

为了对多载波脉宽调制(PWM)技术的谐波特性进行定量的数学分析,通过双重傅立叶变换得到分别采用三种多载波PWM方案的多电平变流器输出电压的傅立叶级数.从谐波品质角度比较了各种方案的优劣,确定了在不同场合下多电平变流器最佳的调制方案.第三种方案的低次谐波含量最低,最适合于单相多电平变流器.在三相平衡无中线系统中,由于载波谐波不产生电流,第三种方案的总谐波失真度最低,因而最为合适.理论分析的结果得到了仿真实验的验证.

In order to perform the quantitative mathematical analysis of the harmonic characteristic in multicarrier pulse width modulation（PWM） technique, the Fourier series of the multi-level converters output voltages with three kinds of multi-carrier PWM strategies respectively were derived by means of dual Fourier transforms. The relative merits of each strategy were analyzed. The optimized modulated strategies under different occasion were determined. The low harmonic component of the third strategy is the lowest, which is the most suitable for single-phase multilevel converters. For three-phase balanced multilevel converters without neutral wire, the first strategy is most suitable due to its lowest total harmonic distortion because the carrier harmonic component does not cause current.