Antiislanding Protection Based on Signatures Extracted From the Instantaneous Apparent Power

This paper proposes a new passive antiislanding method for three-phase (3φ) distributed generation units (DGUs). The proposed method is based on extracting signatures from the instantaneous 3φ apparent powers determined at the point of common coupling (PCC). This new method is found on the fact that the instantaneous 3φ apparent powers have components continuously exchanged between loads and sources. The islanding condition creates transient high-frequency components in the instantaneous 3φ apparent powers.These high-frequency components contain signature information capable of identifying the islanding condition. These transient high-frequency components can be extracted using the wavelet packet transform (WPT), when applied to the direct and quadrature (d-q-axis) components of the instantaneous 3φ apparent powers. The d-q WPT-based antiislanding method is implemented for testing on a 3φ permanent magnet generator-based wind energy conversion system. Test results demonstrate an accurate, fast, and reliable response to the islanding condition occurring when supplying different load types at different levels of power delivery to the host grid.