A Novel Passive Islanding Detection Method Based on Phase-Locked Loop
Abstract
The ever-increasing penetration of distributed energy resources in power distribution systems has led to challenges in the detection of islanding. Among different islanding detection methods (IDMs), passive methods are the least intrusive and typically require the lowest investment cost. However, they generally suffer from larger non-detection zones (NDZs) and higher nuisance detection ratios as compared to active, hybrid, and remote IDMs. This study provides an overview of the criteria outlined in the existing technical literature for the performance evaluation of IDMs, a review and comparison of the existing passive IDMs, and an analysis of the phase-locked loop (PLL) behaviour under grid-connected and islanded conditions using its quasi-static model. Based on the results of these studies, a novel passive IDM is developed that utilizes the PLL error to detect islanding with a small NDZ and high speed.
The performance of the proposed IDM is evaluated under various islanding and non-islanding disturbances. The performance evaluation studies are conducted through simulations in the PSCAD software environment as well as experimental tests using a hybrid microgrid test platform. The study results indicate that the proposed method: (i) can detect islanding in less than two cycles, which is well below the requirements of the IEEE 1547 standard, (ii) leads to a small NDZ and can identify islanding with only ±5% power mismatch, (iii) does not cause false detection of non-islanding disturbances as islanding, and (iv) is robust against noise.