Power electronic transformers (PETs) can be used to interconnect different voltages and forms of electrical systems, and enable to offer higher operation efficiency and flexible power flow controllability. This paper focuses on the fault ride-through (FRT) problem of a PET interconnecting medium voltage (MV) and low voltage (LV) power systems, and the solution of a resistive superconducting fault current limiter (SFCL) is proposed. Firstly, theoretical modeling of the PET and the SFCL is addressed, and a suitable control strategy is applied to realize reliable power exchange between the LV and MV systems. Then, in regards to a fault at the PET's output-terminal, the fault developing process is probed, and considering the SFCL's quench behavior, the PET's current variations are clarified. Further, a 3 MW PET with a SFCL is modeled in MATLAB/Simulink, and through changing the fault severity and the SFCL parameter, different simulations are implemented. The results reveal that the SFCL stabilizes the PET from multiple aspects. A visible current-limiting function is achieved, and the voltage dynamic fluctuations at the AC and DC sides of the PET are effectively alleviated. Meanwhile, the power delivery from the LV to the MV system is smoothed, and a successful FRT fulfillment is gained.

中文翻译：

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用于电力电子变压器互连中低压电力系统故障穿越的电阻式SFCL研究

电力电子变压器（PET）可用于互连不同电压和形式的电气系统，并能够提供更高的运行效率和灵活的潮流可控性。本文重点研究PET互连中压（MV）和低压（LV）电力系统的故障穿越（FRT）问题，并提出了一种电阻超导故障限流器（SFCL）的解决方案。首先，解决了 PET 和 SFCL 的理论建模，并应用了合适的控制策略来实现 LV 和 MV 系统之间的可靠功率交换。然后，针对PET输出端的故障，探讨了故障的发展过程，并考虑SFCL的失超行为，阐明了PET的电流变化。此外，在 MATLAB/Simulink 中对带有 SFCL 的 3 MW PET 进行建模，并通过改变故障严重程度和 SFCL 参数，实现不同的仿真。结果表明SFCL从多个方面稳定了PET。实现了可见的限流功能，有效缓解了PET交直流侧的电压动态波动。同时，从 LV 到 MV 系统的电力传输变得平滑，并获得了成功的 FRT 实现。