Superconducting fault current limiter (SFCL) for fail-safe DC-DC conversion: From power electronic device to micro grid protection

In DC micro grids and networks, DC-DC power converters having a large number of semiconductor-based power electronic devices are usually adopted to interconnect the renewable sources and flexible loads. Most of the semiconductor-based devices suffer from poor fault withstanding abilities, but conventional power electronic protection schemes have the bottlenecks of the time-delay, self-malfunction and mis-judgement. This paper presents a novel solution using the superconducting fault current limiter (SFCL) to protect a power electronic device and extend the usage to a micro grid. This SFCL is actually a self-triggering, recoverable, and passive current limiter, which does not involve any additional circuit hardware and software. Experimental investigations and simulation analyses clarify the feasibility of using this superconductor-based protection scheme to implement the self-acting fail-safe protection of DC-DC converters. Further system-level simulations explore the SFCL to suppress the over-current and stabilize the bus voltage of a photovoltaic based DC micro grid, particularly facing millisecond-level transients and faults. Our experimental and theoretical investigations lay some technical bases to establish a superconductor-semiconductor-coupled interdisciplinary application from the view from the applied superconductivity, to power electronics, and to micro grids.