一种适用于级联H桥整流直流侧电容电压快速平衡的新型调制方法

A Novel Modulation Method for Fast Balancing DC-Link Capacitor Voltages of Cascaded H-Bridge Rectifier

针对无工频变压器大功率多电平变流器级联H桥(Cascaded H-Bridge,CHB)整流级的结构与特点,本文提出了一种使单位功率因数下运行的CHBR在安全工作区的优化工作点上工作的概念以及相应的新型调制策略。该新型调制策略不仅可以使负载突变后CHBR各级联H桥直流侧电容电压达到快速平衡,还可以使CHBR各级联H桥负载的不平衡程度达到最大限度地扩展。本文首先从理论上对于所提优化工作点的概念进行了讨论,然后分析了新型调制策略可以使CHBR各级联H桥直流侧电容电压达到最快平衡的基本原理,同时给出了在此优化工作点下,CHBR各级联H桥负载容许的不平衡程度最大值的定量描述。之后进一步详细讨论了利用CHBR交流侧输出电压与输入电流的极性关系,通过二维调制区域中两条不同的调制轨迹的相互配合,实现新型调制策略的具体方法,最后通过搭建的试验平台验证了该调制方法的正确性和优越性。

Based on the analysis to the structure and features of the cascaded H-Bridge （CHB） rectifier（CHBR） stage of transformerless high power converters, the concept of making CHBR working on optimum point and the corresponding novel modulation method are proposed by this paper. The optimum working point in safety operation area is firstly discussed, and then the principle of fast balancing DC-link capacitor voltages for each cell of CHBR with the novel modulation method is explained in detail, and the quantitative description for the allowed maximum unbalanced loads is also presented. Moreover, the implementation of the proposed novel modulation method which chooses two different modulation curves based on two-dimensional modulation by signs between AC-side output voltage and inductance current is illustrated as well. Finally, experiment results from the prototype test are given, which verified the validity of the proposed novel modulation method.