Protection Circuit for DC Short Fault and Soft-Reclosing Operation for Protective Coordination Algorithm

To protect the power converter station from fault currents during a short-circuit occurrence in DC distribution system, it is important to limit the steep increase of fault currents and isolate the fault section quickly. Since short circuit accidents in the distribution system are almost temporary accidents, it is important to supply DC power to the load without continuing interruption of the power supply after isolation and clearance of fault. Unlike AC systems, DC systems have no zerocrossing current intervals and have a low line impedance characteristic. Consequently, whether the fault is cleared or not, restarting operation in DC system results in the occurrence of switching surges and reclosing current. Accordingly, not only fault detection and protection ability but also an effective reclosing strategy are required for the stability and reliability of DC distribution systems. In this paper, a DC short-circuit fault protection circuit for a DC output converter is proposed, and the analysis and design parameters of the protection circuit is presented. In addition, compared to the conventional reclosing techniques, proposed soft-reclosing enables fast fault detection and stable recovery from transient faults.