Designing and Evaluation of a Hybrid Islanding Detection Method for Inverter-Based Distributed Generation Resources

In Recent advances in renewable energy technologies as well as the restructuring of the electricity market have increased the use of renewable energy resources. The use of these energy sources has many benefits such as increasing reliability, improving power quality, and peak shaving. However, one of the main disadvantages of these energy sources is the islanding detection. The island mode occurs when the main grid is interrupted for any reason, and the part of the grid that contains distributed generation supplies local loads independently from the main grid. Unintentional islanding causes problems such as protective interference and damage to consumer equipment. As a result, the fast detection and disruption of the distributed generation is essential to prevent equipment damaging. This paper presents a new hybrid islanding detection method for distributed generation resources to activate the real power shift method in case the rate of frequency change, in the first stage, exceeds the threshold. Then, if by changing the real part of the DG output current, the voltage amplitude changed, the islanding event would be detected.  The proposed method is implemented and simulated in the Matlab/Simulink environment.  It was also investigated under various conditions such as load switching, motor starting, and multi-DG mode. The simulation results showed the performance of the proposed method in islanding detection in these conditions.