Performance of three islanding detection methods for grid-tied multi-inverters

Islanding occurs when distributed resources continue to power even though electrical power from the utility grid is no longer present. Islanding can be harmful for utility workers, who may not realize that this part is still powered. For the reason of safety hazards and equipment damage due to lack of utility control on voltage and frequency in the island, distributed resources must detect an island and immediately stop producing power.

In this paper, we study the operation of multiple inverters utilizing different active islanding detection methods. The Sandia Voltage Shift (SVS), the Sandia Frequency Shift (SFS) and the Slip Mode frequency Shift (SMS) are used in this work. The study reported is based on MATLAB/Simulink time-domain simulations, taking into account modern international standards. It is shown that a multi-inverter system, which uses three different methods, can detect an island in case of power-matched load. However, it has a reduced performance and slower detection time, compared to single inverter structure.