Impedance characteristics of the floating capacitor in the submodule (SM) of a modular multilevel converter (MMC) change due to its chemical and aging characteristics. This can result in a rise of voltage ripple across SM capacitors, uneven power distribution among the SMs and could also interrupt the operation with prolonged use of degraded capacitors. Existing balancing approaches are presented for the MMC with equal SM capacitance and ignored the effect of capacitor degradation as well as parameter mismatch. Hence, a closed-loop control scheme that incorporates the effect of capacitor degradation is much necessitated. This study aims to overcome this gap by proposing a new power balancing control algorithm for SM capacitors, which effectively controls and evenly distributes the power among SMs. The efficacy of the proposed strategy is substantiated through PLECS simulations and OPAL-RT/OP4510 controller-based experiments on a single-phase MMC laboratory prototype.

中文翻译：

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电容器退化下模块化多电平转换器的子模块功率平衡控制

模块化多电平转换器（MMC）子模块（SM）中的浮动电容器的阻抗特性由于其化学和老化特性而发生变化。这可能会导致SM电容器两端的电压纹波增加，SM之间的功率分配不均，还可能由于长时间使用退化电容器而中断工作。提出了具有相等SM电容的MMC的现有平衡方法，并忽略了电容器退化以及参数失配的影响。因此，非常需要结合电容器退化的影响的闭环控制方案。这项研究旨在通过为SM电容器提出一种新的功率平衡控制算法来克服这一差距，该算法可以有效地控制SM电容器中的功率并使之均匀分配。