H桥级联SVG的载波移相调制技术研究

摘要

Cascade multilevel, high voltage and large capacity inverters have been widely used in electric power systems. Carrier phase shifted sinusoidal pulse width modulation (CPS-SPWM) technique is very suitable for the high power inverter. In the paper, bipolar CPS-SPWM and single pole double frequency CPS-SPWM modulation method are presented respectively, and a simulation model based on PSCAD/EMTDC software is built. Comparative analysis for these two methods is made by adopting frequency spectrum analysis method. Simulation results have proved that the lowest harmonics of the output voltage are centralized near the N times of the carrier frequency, and the equivalent switch frequency is improved by N (N is the number of the cascade SVG for each phase) times by adopting bipolar CPS-SPWM. The lowest harmonics of the output voltage are centralized near the 2N times of the carrier frequency, and the equivalent switch frequency is improved by 2N times by adopting single pole double frequency CPS-SPWM. Therefore, the single pole double frequency CPS-SPWM modulation method is better to eliminate the harmonics, and its output voltage fits sine wave better.%级联多电平高压大容量变流器已广泛应用于电力系统中，载波移相式正弦脉宽调制（CPS-SPWM）技术非常适用于大功率变流器场合。文中分别介绍了双极性CPS-SPWM调制方法和单极倍频CPS-SPWM调制方法，并基于PSCAD/EMTDC软件搭建仿真模型，采用频谱分析方法对其进行对比，结果表明采用双极性CPS-SPWM调制方法输出电压的最低次谐波群出现在N（N是指每相级联单元数）倍的载波频率附近，其等效开关频率提高了N倍，采用单极倍频CPS-SPWM调制方法的输出电压的最低次谐波群出现在2N倍的载波频率附近，其等效开关频率提高了2N倍，因此采用单极倍频CPS-SPWM调制方法其输出波形更接近正弦波，具有更好的消除谐波的特性。