A novel anti-islanding detection algorithm for three-phase distributed generation systems

This paper presents a novel anti-islanding (AI) detection algorithm for three-phase (3Φ) grid-interface converters in distributed generation systems. A generic phase-locked loop (PLL) model by considering the converter interaction with grid is proposed. And the frequency positive-feedback mechanism is proposed to predict the frequency behavior of the grid-interface converter system, especially under the islanded condition. Many of the frequency-related behaviors can be well explained and the crucial system parameters, which impact the PLL stability and non-detection zone (NDZ), can be also quantified by the proposed model. Based on the model, a novel anti-islanding detection algorithm based on the frequency stability is proposed to effectively detect the islanding event under the worst loading condition, achieving ideally a zero NDZ. The proposed algorithm features a small impact to the converter system operation as well as a easy implementation.