This article proposes an isolated dc-dc modular multilevel converter (MMC) topology intended for tapping power from the high-voltage dc (HVdc) link. The proposed converter operates with two stages of power conversion, i.e., HVdc to ac and ac to medium-voltage dc, using an intermediate medium-frequency transformer. The proposed topology reduces the number of arms in MMC to two, along with a series LC passive filter tuned at a medium frequency at the primary side of the transformer. A high-voltage transformation ratio is possible in the proposed converter. Operation at the medium-frequency ac ensures the reduction in the size of the transformer and other passive elements. A sinusoidal level-shifted pulsewidth modulation technique is implemented for modulating the arm voltages of the converter, which results in a voltage close to the sine wave with small dv/dt being impressed across the transformer primary. The design of the passive filters is also included in the article. The operation of the converter is validated by the simulation of a 400 kV, 10 MW system, and a downscaled experimental prototype of 1 kW, 400 V system.

中文翻译：

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模块化多级 DC-C 电源转换器拓扑，具有用于 HVDC 分接的中频交流级


本文提出了一种隔离式 DC-DC 模块化多电平转换器 (MMC) 拓扑，旨在从高压直流 (HVdc) 链路获取功率。所提出的转换器使用中间中频变压器进行两级功率转换，即高压直流到交流和交流到中压直流。所提出的拓扑将 MMC 中的臂数量减少到两个，并在变压器初级侧以中频调谐串联 LC 无源滤波器。在所提出的转换器中可以实现高电压变压比。在中频交流电下运行可确保减小变压器和其他无源元件的尺寸。采用正弦电平移位脉宽调制技术来调制转换器的臂电压，从而在变压器初级上施加一个接近正弦波且具有较小 dv/dt 的电压。本文还包括无源滤波器的设计。通过模拟 400 kV、10 MW 系统和缩小规模的 1 kW、400 V 系统实验原型验证了转换器的运行。