Battery-equipped apparatuses, such as electric vehicles (EVs), renewable energy generations, and mobile devices, are widely used and still being developed. For the design and evaluation of these devices, there is a growing demand for dc power supplies to test the charge-discharge characteristics and lifetimes of batteries. As the voltage and performance of the batteries increase, the power supplies for the battery test must be able to handle higher voltages and have a faster output transient response. To handle a high voltage, multilevel converters that use multiple power devices with lower voltage ratings have often been used in recent years, in addition to using a single power device with high-voltage ratings. Among various circuit topologies, modular multilevel converters (MMCs) have been actively studied and developed. However, unlike dc-ac and ac-dc conversions, dc-dc conversion in MMCs has a problem in that the cell capacitor voltages cannot be balanced in principle because of less redundancy of operation states. Therefore, most MMC-based dc-dc converters achieve voltage balancing control by combining a dc-ac conversion, isolation transformer or inductor, and ac-dc conversion. However, these circuit configurations tend to have a large equivalent inductance and are unsuitable for achieving a fast output response. In this study, we analyze the dc-dc operation and its problems in the MMC circuit. Based on the analysis, a circuit topology using auxiliary inductor circuits and a control method suitable for a dc-dc converter are proposed. A prototype of a 6-cell MMC-based dc-dc converter using SiC-MOSFETs was designed and implemented, and it was demonstrated that cell voltage balancing control and fast output response could be realized.

中文翻译：

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具有辅助电感电路的模块化多电平 DC-DC 转换器，用于电池电压平衡和快速输出响应


电动汽车（EV）、可再生能源发电和移动设备等配备电池的设备已被广泛使用且仍在开发中。为了设计和评估这些设备，对直流电源测试电池充放电特性和寿命的需求不断增长。随着电池电压和性能的提高，用于电池测试的电源必须能够处理更高的电压并具有更快的输出瞬态响应。为了处理高电压，除了使用具有高额定电压的单个功率器件之外，近年来还经常使用使用具有较低额定电压的多个功率器件的多电平转换器。在各种电路拓扑中，模块化多电平转换器（MMC）已被积极研究和开发。然而，与dc-ac和ac-dc转换不同，MMC中的dc-dc转换存在一个问题，即由于操作状态冗余较少，单元电容器电压原则上无法平衡。因此，大多数基于MMC的DC-DC转换器通过结合DC-AC转换、隔离变压器或电感器以及AC-DC转换来实现电压平衡控制。然而，这些电路配置往往具有较大的等效电感并且不适合实现快速输出响应。在本研究中，我们分析了 MMC 电路中的 DC-DC 操作及其问题。基于分析，提出了一种使用辅助电感电路的电路拓扑和一种适合dc-dc转换器的控制方法。设计并实现了使用 SiC-MOSFET 的基于 6 单元 MMC 的 DC-DC 转换器原型，并证明可以实现单元电压平衡控制和快速输出响应。