Protection of low voltage AC microgrid using discrete wavelet transform

To protect microgrids the variation in fault level poses a significant challenge. In this paper, a wavelet energy-based protection scheme is proposed to detect the fault. The sum of the squared differential current in all three phases is passed to DWT (discrete wavelet transform) filter bank. The wavelet coefficients are obtained using the signal processing technique (DWT) and the energy of the extracted wavelet coefficients is calculated. When wavelet energy exceeds the threshold limit, it is considered an internal fault else it is an external fault or external disturbance. The microgrid's performance was estimated by taking several parameters like different fault types, fault locations, fault resistances, and external fault and non-fault conditions (capacitor and load switching). The microgrid was modeled in MATLAB/Simulink environment. A comparison has been done between the differential protection scheme and the proposed wavelet energy-based scheme. The proposed wavelet energy protection scheme detected faults in 6 ms and provided reliable results in detecting faults for low-voltage AC microgrids. The simulation results indicate that a wavelet energy-based scheme can be implemented to enhance the protection of the microgrid.