Performance of the Phaselet Frames-Based Digital Protection for Distributed Generation Units

This paper presents the development and performance evaluation of a digital protection for interconnected distributed generation units (DGUs). The developed protection detects and responds to transient disturbances (fault and nonfault conditions) based on the magnitudes and phases of the high-frequency sub-band contents, which are extracted from the d-q-axis components of the currents flowing through the point-of-common-coupling (PCC). These magnitudes and phases are extracted by six phaselet frames that are realized by a modulated filter bank that is composed of six digital high-pass filters (HPFs). The coefficients of HPFs are determined by biorthogonal phaselet basis functions. Extracted magnitudes and phases of the high-frequency sub-band contents of PCC d-q-axis current components provide signature information for accurate detection and identification of faults. The performance of phaselet frames-based digital protection is experimentally tested for two wind energy conversion systems (WECSs) and a photovoltaic (PV) system under different fault and nonfault conditions. Test results demonstrate reliable and timely responses, along with negligible sensitivity to the type and control of DGUs, type and location of faults, and loading levels.