Robust Adaptive Active Islanding Detection With $\alpha$-Axis Disturbance Injection Under High Impedance Fault, Unbalanced Loading, and Phase Failure in Grid Tied PV System

Power generation with PV technology is growing expeditiously. With the high penetration of solar-based generation, a concern of islanding detection is always by the distributors due to grid side faults and abnormality. It is the demand of the situation to equip the PV-connected inverter with an islanding detection mechanism to avoid any catastrophe. In the present work, an active islanding detection technique utilizing a smaller magnitude current injection through
$\alpha$
-axis current controller of grid side voltage source converter (VSC) is proposed. Due to injection of current through VSC, point of common coupling (PCC) voltage is having different harmonic component in the grid connected and islanded mode. In the proposed detection method, the sensed PCC voltage is used to derive the three signals, i.e., absolute
$v_{\text{mag}}$
variation mean, absolute mean of square variation of
$v_{\text{mag}}$
, and frequency of absolute
$v_{\text{mag}}$
variation mean. These three derived signals are used to take the decision for islanding detection. Further, complex coefficient filter—second order frequency locked loop is proposed for three phase grid synchronization and frequency estimation. The proposed strategy is tested under high impedance fault, phase failure, and unbalanced loading conditions. It is found that the proposed work clearly differentiates the islanding and faults condition. The nondetection zone of the proposed strategy is verified under different quality factors (
$Q_{f}$
) of the load. To evaluate the effectiveness of the suggested strategy, MATLAB Simulation and experimental validation is performed. The obtained islanding detection time is within the IEEE-1547 standard.