Modeling and Control Method for a Three-Level Hybrid Modular Multilevel Converter
Modeling and Control Method for a Three-Level Hybrid Modular Multilevel Converter
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DOI：
10.1109/tpel.2021.3118425
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发表时间：
2022-03
影响因子：
6.7
通讯作者：
Jian Liu;Di Zhang;D. Dong
中科院分区：
文献类型：
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作者：
Jian Liu;Di Zhang;D. Dong
模块化多电平变换器（MMC）是中高压应用中最受欢迎的拓扑结构之一。然而，缺点，如大量的电容器和加倍的设备数量，限制了功率密度。最近提出的带有高压开关和链环的混合多电平变换器与传统的MMC相比表现出了优越的性能。具体来说，本文重点介绍了一种新型的三电平混合模块化多电平变换器，该变换器可以将子模块数量减少一半。在此基础上，推导了一个解耦平均模型，揭示了三层堆叠和链链之间的内部功率关系。可以证明前者起到了将一部分功率直接从直流侧转移到交流侧的作用。因此，链环的能量变化较小，可以减小直流链的电容。此外，采用改进的梯形臂电流分配方法解决了电压过零处的臂电流畸变问题。为了保证手臂电流跟踪性能，提出了基于变采样重复控制的电流环设计。最后，400-V样机的实验结果验证了所提出的建模和控制方法。
The modular multilevel converter (MMC) is one of the most favored topologies for medium and high voltage applications. However, the drawbacks, such as lots of capacitors and doubled number of devices, limit the power density. Recently proposed hybrid multilevel converters with high voltage switches and chain-links have shown the superior performance compared with the traditional MMC. Specifically, this article focuses on an emerging three-level hybrid modular multilevel converter, which can reduce half of submodule number. Based on the operating principle, a decoupling average model is derived to reveal the internal power relationship between the three-level stacks and chain-links. It can be proven the former plays a role to transfer a part of power from dc side to ac side directly. Therefore, the energy variation of chain-link is smaller, and the dc-link capacitance could be reduced. Besides, an improved trapezoidal arm current allocation is employed to solve the arm current distortion at the voltage zero-crossing point. In order to guarantee the arm current tracking performance, the variable sampling repetitive control based current loop designs are proposed. Finally, the experimental results of a 400-V prototype validates the proposed modeling and control methods.