An improved method for single-phase voltage drop detection

The response speed of dynamic voltage restorer (DVR) is an important indicator to evaluate its performance, and the detection of transient voltage sags is a key factor affecting the response speed. The imbalance of grid voltage constrains the accuracy and rapidity of both the phase-locked loop and detection algorithms. In order to address the issues of low accuracy and poor dynamic performance of traditional voltage sag detection methods, an improved instantaneous symmetrical component method is applied to extract symmetrical three-phase fundamental positive-sequence components from the unbalanced three-phase voltage after sag occurrence. These components are then fed into the phase-locked loop for synchronization, thereby enhancing the accuracy and dynamic performance of the detection method. Simulation and experimental results demonstrate that the proposed method achieves high accuracy and fast response speed.