三电平变流器直流电压平衡控制方法

为研究三电平变流器直流电压平衡的问题 ,建立了三电平变流器的数学模型 ,详细分析了空间矢量脉宽调制(PWM)的特性和直流环电容电压平衡调节的基本原理 ,提出了一种新型的基于交流电流方向检测的直流电容电压平衡控制方法。该方法通过实时检测三相交流输出电流方向得到方向函数 ,利用该函数选择一个 PWM周期内不同电压矢量作用时间来控制中点电流的方向 ,实现电压平衡。该方法可以使得直流电容电压的平衡不受变流器功率因数过低和功率流向的影响。

DC voltage balance control method for three-level converter

A mathematical model was presented to investigate the DC voltage balance of three -level converter systems. The theory for the space -vector pulse -width modulation (PWM) method and the DC voltage balance were analyzed for three -level converters. A new DC voltage balancing control method was proposed that detected the AC current direction to balance the DC voltage. By getting the direction function from the output AC current, the applied time of voltage vectors in one PWM period was chosen, the direction of central current was controlled for DC voltage balance. This method was not influenced by a low power factor of the converter or the direction of the active power. Experimental results verify the feasibility of this method.