Study On Resistive SFCL for Fault Ride-Through Fulfillment of Power Electronic Transformer Interconnecting MV and LV Power Systems

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.