The development and testing of a coordinated anti-islanding protection for collector systems with multiple distributed generation units

This paper presents a coordinated anti-islanding protection for collector systems with multiple distributed generation units (DGUs). The presented anti-islanding protection is established based on processing the d-q-axis components of the instantaneous three phase apparent powers (sd and sq), determined at the point-of-common-coupling, using the wavelet packet transform (WPT). Processing sd and sq by using WPT allows the extraction of low and high frequency sub-band contents. The contents of the high frequency sub-band are used to detect and distinguish islanding events, and contents of the low and high frequency sub-bands are employed to define a coordination index, which is used to identify the islanded DGU(s). The presented anti-islanding protection is implemented for off-line testing using data obtained from a laboratory collector with four different DGUs. Off-line test results demonstrate accurate, fast, and reliable responses to islanding and non-islanding event(s), accurate identification of islanded DGUs, along with negligible sensitivity to levels of power delivery to the collector system.