Since the introduction of modular multilevel converters (MMC), various additional features have been introduced for MMCs, among them parallel inter-module connectivity. However, such a parallel mode requires appropriate modulation and switching strategies to exploit its full potential. Low-frequency switching modulation is widely used with half-bridge modules and a large body of research focusses on the optimum control and scheduling of these methods. However, so far, a suitable adaptation for MMCs with parallel mode is missing, and existing methods perform suboptimum. This article proposes a generic scheduling algorithm for simple and low-cost integration with low-frequency switching modulation. The proposed method reduces control complexity, minimizes power loss, and can be combined with most modulation techniques, including nearest-level modulation (NLM) and selective harmonic elimination. The text in this article provides a general algorithm for integrating this method with other control levels and analyzes its effect on MMCs with parallel functionality. Moreover, it examines the performance of the system with NLM combined with the proposed scheduler and compares it to other alternatives. Results show up to a 50% reduction in power loss with a similar modulation technique as well as significantly lower THD and power loss compared to optimized phase-shifted carrier modulation as another sensorless alternative method.

中文翻译：

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具有并行功能的模块化多电平转换器中低频开关的通用调度算法

自从引入模块化多电平转换器 (MMC) 以来，已经为 MMC 引入了各种附加功能，其中包括并行模块间连接。然而，这种并行模式需要适当的调制和切换策略来充分发挥其潜力。低频开关调制广泛用于半桥模块，大量研究集中在这些方法的最佳控制和调度上。然而，到目前为止，缺少对具有并行模式的 MMC 的合适适配，并且现有方法执行次优。本文提出了一种通用调度算法，用于与低频开关调制进行简单、低成本的集成。所提出的方法降低了控制复杂度，最大限度地减少了功率损耗，并且可以与大多数调制技术相结合，包括最近电平调制 (NLM) 和选择性谐波消除。本文中的文本提供了一种将此方法与其他控制级别集成的通用算法，并分析了其对具有并行功能的 MMC 的影响。此外，它使用 NLM 结合建议的调度程序检查系统的性能，并将其与其他替代方案进行比较。结果表明，与作为另一种无传感器替代方法的优化相移载波调制相比，使用类似调制技术可将功率损耗降低多达 50%，并且显着降低 THD 和功率损耗。它使用 NLM 结合建议的调度程序检查系统的性能，并将其与其他替代方案进行比较。结果表明，与作为另一种无传感器替代方法的优化相移载波调制相比，使用类似调制技术可将功率损耗降低多达 50%，并且显着降低 THD 和功率损耗。它使用 NLM 结合建议的调度程序检查系统的性能，并将其与其他替代方案进行比较。结果表明，与作为另一种无传感器替代方法的优化相移载波调制相比，使用类似调制技术可将功率损耗降低多达 50%，并且显着降低 THD 和功率损耗。