A novel protection scheme for inverter-dominated microgrid

Protecting an inverter-dominated microgrid is challenging for the traditional overcurrent protection scheme owing to the suppressed fault current from the inverter interfaced DGs (IIDGs). In this paper, a protection scheme based on the Discrete Wavelet Transform is developed in MATLAB/SIMULINK to detect the faults in the microgrid. The input voltage of the proposed scheme is first transformed into dq0 frame using the Park Transform. A filtering system based on the wavelet denoising approach is then implemented to reduce the sampling frequency and reject the switching noise generated by the inverters in the microgrid. The performance of the proposed scheme is evaluated in transient simulation by systematically applying different types of faults, including varied fault positions and impedances. Additionally, a high impedance arcing fault model is implemented to test the proposed protection scheme under nonlinear fault impedance conditions.