A Symmetrical-Structure Fault Current Limiter for Bipolar DC Distribution Networks

In a bipolar DC distribution network, both the pole-to-ground fault (PGF) and the pole-to-pole fault (PPF) would threaten its security and stability. This paper proposes a symmetrical-structure fault current limiter (SSFCL) topology, which can help achieve fault riding through (FRT) of PGF and PPF in a bipolar DC distribution network. With the SSFCL, the rising speed of the fault current can be limited, thus ensuring the safety of the DC transformers (DCTs). Then the fault current can be hysteresis controlled within a required range, which provides an adequate fault criterion to locate the faulty load branch. The discharging path of the SSFCL can create a fault current zero point, enabling the solid-state switches to achieve zero-current switching (ZCS) when cleaning the faulty branch. In addition, with the SSFCL, the terminal voltages of the DCTs would not decay during the FRT process, which ensures the fast restoration of the power supply after the fault has been cleaned. The effectiveness of the SSFCL is verified on a ± 375 V bipolar DC experimental prototype. The SSFCL presented in this article provides a solution for the DC fault in a bipolar DC distribution network.