A Novel Flexible Fault Current Limiter for DC Distribution Applications

As an effective carrier of new energy collection, DC power grid has characteristics of low inertia and weak damping, which makes DC fault propagate extremely fast. However, the existing protection and DC circuit breaker (DCCB) technique still could not match its fault propagation speed. Therefore, to solve this problem, a novel of flexible fault current limiter (NFFCL) is presented in this paper. Under normal operation condition, NFFCL is connected to DC line in series without negative influence. When a fault occurs to DC line, NFFCL's rectifier circuit, according to the protection criterion, provides cascade inductor, which is connected to DC line in series, with a set-slope linear current. In this case, the voltage drop between both ends of inductor can be clamped flexibly, which can even completely isolate the fault area. A controlled voltage source (CCVS) is applied to generate inverse flux to prevent the cascading inductor from magnetic saturation. When the fault disappears, the energy of current-limit inductor can be released and transferred to AC power grid through NFFCL's converter. Finally, simulation cases are carried out to verify the working principles and practicability of proposed NFFCL.