Development of passive anti-islanding strategies for distributed generation systems
University of New Brunswick
Detecting and removing islanding operation are necessary for the large-scale deployment of distributed generators (DGs) in electric power systems (EPS), as mandated by different standards and industrial practices. Although passive islanding detection techniques have no impact on EPS functions, they possess a shortcoming characterized by a large non-detection zone (NDZ) over which islanding detection may fail, resulting in unsafe operation and non-compliance with the interconnection standards. New anti-islanding detection and protection methods are developed and presented in this dissertation, which focus on the operating space where existing methods fail. The developed techniques aim to realize reliable and timely islanding detection overall operating conditions. The frequency dependent impedance (FDI) concept is presented as a means of islanding detection that is based on spectral decomposition of voltage and current at the point of comment coupling (PCC). The impedance frequency technique (ZFT) concept is presented as a new anti-islanding algorithm. In addition, a passive anti-islanding algorithm, which is independent from the power electronic converter (PEC) and is based on the virtual power signal (VPS) with improved anti-islanding performance, is introduced and tested online. Furthermore, the zero sequence impedance (ZSI) concept is a new passive anti-islanding algorithm that is developed employing the wavelet packet transforms (WPT). The ZSI algorithm is reliable and timely for detecting the islanding operation, and may be applied for DG systems with PECs and DG systems without PECs. The developed methodologies are explored analytically, validated in simulation, and tested experimentally. Performance results demonstrate the effectiveness of the proposed anti-islanding methods in comparison with existing methods.