说明：  在MATLAB环境下，分别建立了5、7、9级MMC直流传输模型，验证了CPS-SPWM模式的特性。结果表明，对于低电平MMC变换器，PWM具有良好的逼近调制波的能力，谐波分量少，等效开关频率低。
(In the MATLAB environment, MMC DC transmission models of 5, 7 and 9 levels are built respectively, and the characteristics of CPS-SPWM mode are verified. The results show that for low-level MMC converter, PWM has a good ability to approach the modulation wave, with less harmonic components and less equivalent switching frequency rate)