Voltage dips detection in a microgrid with distributed generation for grid-tie inverter protection purposes

The paper addresses the problem of fault detection in an unbalanced microgrid with distributed generators, using algorithms based on harmonic estimation: Wavelet Transform (WT), Fast Fourier Transform (FFT) and Reduced Fast Fourier Transform (RFFT). Simulations were carried out in the MATLAB/SimPowerSystems environment. Modified IEEE13 bus system with distributed generation was used. Experimental verification was done in the Laboratory for Power Electronics of the Faculty of Technical Sciences on advanced setup with grid emulator and modern hardware using modified industrial converters and advanced control circuit. The algorithms were evaluated as part of the grid-tie inverter protection scheme for 6 types of faults. It was shown that wavelet with Daubechies with 4 filter coefficients has not performed as expected, as it was not able to successfully detect voltage dips. On the other hand, algorithms based on Fourier transformation (FFT and RFFT) successfully detected voltage dips.