Anti-islanding protection in three-phase converters using grid synchronization small-signal stability

This paper presents the islanding detection algorithms for three-phase (3Φ) grid-interface converters based on the grid synchronization small-signal stability. To study the grid synchronization behavior at the islanded condition, a low-frequency small-signal phase-locked-loop (PLL) model is proposed by considering the converter interaction with the system impedances. Many of the frequency-related behaviors can be well explained and the crucial system parameters which impact the PLL stability are quantified by the proposed model as well. Based on the model, two islanding detection algorithms based on the small-signal stability theory are proposed to effectively detect the islanding event under the worst loading condition. The proposed algorithms feature a small impact to the converter system operation as well as an easy implementation. Multi-disciplinenary comparison and the detailed design procedures are given.