Fault Location Method for Flexible DC Distribution Networks

In flexible DC distribution networks, converter stations are difficult to withstand bipolar short-circuit surge currents, locking out within 1-2 ms, providing little effective information for fault location, resulting in poor positioning accuracy. Therefore, a fault location method based on DC/DC active injection for flexible DC distribution networks is proposed. Under the condition that all converter stations are locked, metal faults unlock the DC/DC converter station at the head of the network, while non-metallic faults successively unlock the DC/DC converter stations at both ends, and then voltage and current data are extracted for fault location. This fault location method considers the issue that converter stations cannot provide effective transient information due to rapid locking. By utilizing the electrical characteristic response of the high-voltage side support capacitor of the DC/DC converter station to the injected signal, the fault section can be distinguished. Moreover, this method does not require additional injection equipment and is suitable for networks with a single MMC converter station, with a simple and reliable principle and high positioning accuracy. Finally, a flexible DC distribution network was built in PSCAD/EMTDC simulation software to verify the feasibility of the proposed fault location method.