Superimposed modal voltage based passive islanding detection of grid tied distributed generation using Wigner distribution function

The integration of distributed generation (DG) into modern electric grids has garnered considerable interest due to its potential to enhance energy resiliency, reduce carbon emissions, and improve security. However, a critical challenge arises in the form of unintentional islanding. Islanding refers to a situation when DG systems, disconnected from the main network, continue supplying nearby loads. Such events pose risks to grid stability by resulting in deviations in voltage and frequency levels, equipment damage, and network safety. To address these challenges, this study introduces a novel approach for detecting islanding events in grid-tied DG systems using Wigner distribution functions and alienation index. First, a modal voltage signal is extracted from three-phase voltage measurements. Next, delta filters capture superimposed components of modal voltage. An islanding detection index (IDI) is then developed by utilising the Wigner distribution and alienation coefficient to effectively characterize islanding signatures. Finally, the IDI is evaluated against a predetermined threshold to differentiate islanding events from non-islanding conditions. Simulations are performed in MATLAB/SIMULINK on a standard IEC microgrid to validate the effectiveness of the proposed method. The results show superior performance over traditional techniques in speed, accuracy, and non-detection zones.