Apparent Power-Based Anti-Islanding Protection for Distributed Cogeneration Systems

In this paper, the performance of a passive anti-islanding method is experimentally tested for three phase (3 phi) cogeneration systems. The tested method is based on determining the wavelet packet transform (WPT) high-frequency subbands present in the d-q-axis components of instantaneous 3f apparent powers (s(d) and s(q)), when evaluated at the point of common coupling (PCC). This passive anti-islanding method is founded based on the nature of instantaneous 3f apparent powers that have components continuously exchanged between both sides of the PCC. An islanding condition can be considered as a transient disturbance that creates nonperiodic and nonstationary high frequency components in sd and sq. These frequency components can be parameterized by WPT high-frequency subbands, which can provide accurate detection of the islanding condition. The d-q WPT-based anti-islanding method is tested for a 3 phi cogeneration system under various loading and power delivery conditions. Performance results reveal accurate, fast, and reliable detection and response to the islanding condition.