이경민(Kyung-Min Lee) ; 박철원(Chul-Won Park)
LVDC Microgrid is a small-scale power grid that can increase the stability and efficiency of power supply in a small area, enabling independent operation and increasing the acceptability of DERs (Distributed Energy Resources). However, this is an ungrounded IT (Isolated Terre) grounding system, and even when a ground fault occurs, there is no fault current path and no significant difference compared to the steady state current, so fault detection is very difficult. WT (Wavelet Transform), an easy tool for transient analysis and signal identification, is to be applied to the detection of ground faults in LVDC Microgrid.
In this paper, we propose a Wavelet transform-based ground fault detection method for an ungrounded LVDC Microgrid. By changing the level and order of various MW (Mother Wavelets) using the current collected in the existing pulse injection method, the optimal MW for ground fault detection method is derived. First, an ungrounded LVDC Microgrid is modeled using PSCAD s/w, and ground faults are simulated by varying the fault point and fault resistance. We implement the selected optimal Wavelet transform-based ground fault detection method using Matlab s/w. Finally, performance evaluation is performed through simulation using various collected signals