Passive Islanding Detection Scheme Based on Instantaneous Voltage and Current for a Multi-DG Microgrid

Abstract

The electricity grid has been transforming since its inception. The increase in carbon emissions and scarcity of fossil fuels has led to using renewable energy sources for power generation. In recent times, microgrids have been gaining popularity, as they can connect to the grid or disconnect from the grid to supply power to the local loads during grid failure and calamities. The presence or absence of the utility grid is crucial to the overall operation of the microgrid. This paper focuses on early islanding detection by considering the instantaneous values of phase voltage and line currents. In the proposed method, the relative position of voltage and current signals are monitored, and a coincidence index keeps track of any change in their relative positions. During the grid-connected operation, the coincidence index remains low. However, when the grid is disconnected, the coincidence index rises. Islanding is detected when the coincidence index crosses a fixed threshold. MATLAB/Simulink-based simulation studies were carried out on the IEEE 13 bus system to check the effectiveness of the proposed Instantaneous Islanding Detection technique during normal operation, faults, switching of loads, and switching of Distributed Generators. It was found that the proposed scheme could detect islanding in less than one-fourth of the cycle and has a low non-detection zone. Also, during the evaluation, the proposed instantaneous islanding detection technique identified islanding much earlier than existing methods.

Keywords

• Renewable energy
• distributed generation
• microgrids
• islanding
• passive islanding detection
• voltage source converter