This article presents a novel flux-cancellation-based modular multilevel converter (MMC) with power decoupling capability. Conventional MMC suffers from low-frequency (fundamental and second-order) ripple power in the submodule (SM) capacitors. The low-frequency ripple power makes the SM capacitors bulky, responsible for a significant portion of the volume and weight of the whole system. The ripple power on the SM capacitor of the three-phase module is phase-shifted by $2\pi $ /3 rad from each other. The proposed flux cancellation is based on directing the low-frequency ripple power to a common core of a three-winding transformer to cancel out. A three-port bidirectional isolated dual half-bridge is introduced for flux cancellation. For this scheme, the main problem is the presence of leakage inductances of the transformer, and another one is three-port isolated bidirectional converter modeling as it has only input ports. The average model is proposed for the flux cancellation circuit. It provides a practically simple model for the complex circuit. Second, a virtual-capacitance-based power decoupling controller is proposed to overcome the leakage inductance problem by the benefits of simple current estimation and of no need for the current sensor. The proposed power decoupling method reduces the system size significantly and enables the MMC to operate with a nonelectrolytic SM capacitance of few microfarads. The operating principle and control design of the proposed MMC are presented. The proposed MMC is validated by simulation and experimentation.

中文翻译：

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一种新型的磁功率去耦的无电解MMC电容器

本文提出了一种具有功率去耦功能的新型基于通量抵消的模块化多电平转换器（MMC）。常规MMC遭受子模块（SM）电容器中的低频（基本和二阶）纹波功率的困扰。低频纹波功率使SM电容器体积庞大，占整个系统体积和重量的很大一部分。三相模块的SM电容器上的纹波功率通过以下方式相移 $ 2 \ pi $ 彼此之间为/ 3 rad。拟议的通量抵消是基于将低频纹波功率引导至三绕组变压器的公共磁芯以抵消。引入了三端口双向隔离双半桥来消除通量。对于这种方案，主要问题是存在变压器的漏感，另一个问题是三端口隔离双向转换器建模，因为它只有输入端口。提出了磁通抵消电路的平均模型。它为复杂电路提供了一个实用的简单模型。其次，提出了一种基于虚拟电容的功率去耦控制器，以通过简单的电流估计和不需要电流传感器的优点克服漏感问题。拟议的功率去耦方法可显着减小系统尺寸，并使MMC能够以几微法拉的非电解SM电容工作。介绍了拟议的MMC的工作原理和控制设计。通过仿真和实验验证了提出的MMC。