Fault distance estimation-based protection scheme for DC microgrids

The DC microgrid has become a typical distribution network due to its excellent performances. However, a well-designed protection scheme still remains to be a challenge for DC microgrids. This paper proposes a fault distance estimation-based protection scheme for DC loop-type microgrids relying on two-terminal electrical quantities. Different from the traditional methods, a small inductor is implemented at each head of the line instead of obtaining the derivative of fault current using current difference value. Thus, the derivative of currents can be calculated accurately with the measured voltages on the small inductors during faults. The presented protection method is able to realise fault location and fault isolation quickly and accurately. Furthermore, it is immune to fault resistances. The presented protection scheme has been tested and verified through PSCAD/EMTDC simulations. The results prove that the new protection scheme possesses the excellent performance.