Introducing a New Hybrid Method with Second Generation Wavelet Transform and Sandia Frequency Shift for Islanding Detection of Inverter-Based Distributed Generation

This paper is introducing a new controlling scheme with second generation wavelet transform and sandia frequency shift (SFS) for islanding detection of inverter-based distributed generation. This new hybrid method combines two active and passive methods through two performance zones. The new hybrid method calculates energy entropy of wavelet coefficients in its passive zone and if it increases from a predefined threshold¡ the method goes into its active performance zone which is implemented by SFS method. In the active performance zone if the frequency of PCC is beyond the range which is defined in the standards¡ islanding condition can be detected by frequency relays otherwise the hybrid method will back to its passive performance zone. The new hybrid islanding detection method uses second generation wavelet transform (lifting scheme) which allows faster implementation of wavelet calculations. The advantage of the new method compared to passive methods is reduction of non-detection zone and also compared to active methods is reducing injection of disturbances into the system. All simulation results have been done in MATLAB/Simulink software. The results confirm the idea which is presented in this paper.