Single-phase islanding detection based on phase-locked loop stability

Active islanding detection schemes are useful to avoid energizing local power systems during fault and grid failure conditions. These types of islanding conditions not only lead to unsafe and unreliable power delivery to the loads and grid, but can cause damage to equipment as well as raising safety concerns for workers and users. This work presents a method of active islanding detection for single-phase converter systems via the stability of a controller´s phase-locked loop. This method inherently detects islanding conditions without applying perturbations at the converter output to test for islanding conditions-as other active methods do-thus avoiding the injection of distortions into the grid. Analytical, simulated and experimental results are presented for verification of the proposed method.