Abstract This paper studies MMC-based non-isolated DC/DC converter for DC transmission grids. The key design parameters including operating frequency and size of passive components are evaluated with the aim of ensuring DC fault tolerance and minimizing losses and size. An analytical model is used to perform parametric studies while detailed non-linear model is used for verification. The case study on 600MW, 320 kV/250 kV system reveals the narrow range of optimal cell capacitance and arm inductance while lower-side arms require substantially larger capacitors. With the targeted losses of 1.5%, and voltage ripple of ±5%, it is recommended to use around 150 Hz operating frequency. For the offshore applications, higher frequency enables significantly smaller size with some increase in losses. The line inductor on the low-voltage side should be much larger than the arm inductor and plays a key role in the dc fault responses.

中文翻译：

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直流容错非隔离大功率MMC DC/DC变换器的频率和参数选择

摘要 本文研究了用于直流输电网的基于MMC 的非隔离DC/DC 转换器。评估包括工作频率和无源元件尺寸在内的关键设计参数，目的是确保直流容错并最大限度地减少损耗和尺寸。分析模型用于执行参数研究，而详细的非线性模型用于验证。对 600MW、320 kV/250 kV 系统的案例研究揭示了最佳电池电容和臂电感的范围很窄，而下臂需要更大的电容器。目标损耗为 1.5%，电压纹波为 ±5%，建议使用 150 Hz 左右的工作频率。对于海上应用，更高的频率可以显着减小尺寸，但会增加一些损耗。