基于正交虚拟矢量的单相MMC系统环流抑制方法

Orthogonal virtual vector based circulating current reducing method for single-phase MMC system

现有的模块化多电平换流器(MMC)的研究大多集中在三相系统方面。提出了一种针对单相MMC系统的基于正交虚拟矢量的新型环流抑制方法,通过分析单相MMC系统环流的固有特点,利用陷波器提取二倍频环流分量,再引入1/4周期延时构造正交虚拟矢量,最终使用比例积分控制器进行环流抑制。此方法不仅能够显著降低桥臂电流的畸变,而且可以减少直流侧的瞬时功率波动,降低了测量器件的数量与成本。仿真和实验结果验证了所提方法的有效性。

The existing studies of MMC （Modular Multilevel Converter） are mostly focused on three-phase systems. A novel circulating current reducing method based on an orthogonal virtual vector is proposed for single-phase MMC system. The inherent characteristics of single-phase MMC system are analyzed, a notch filter is used to obtain the double frequency circulating current component,a 1/4 periodical delay is introduced to produce the orthogonal virtual vector, and the circulating current is finally reduced by proportional-integral controllers. The proposed method can not only significantly reduce the distortion of the arm current, but also decrease the instantaneous power fluctuation of DC side and reduce the number and cost of measuring devices. Simulative and experimental results verify the effectiveness of the proposed method.