Impact of grid background harmonics on inverter-based islanding detection algorithms

The capability of islanding detection has become a requirement for grid connection of inverters utilized in distributed generation (DG) systems. The parallel RLC resonant circuit comprised, as a local load, in the standard test of islanding detection schemes offers lower impedance for higher frequency harmonics. With the presence of such a parallel RLC circuit, the full power balance between the distributed generation and local load will never be satisfied when the voltage at the point of common coupling is slightly distorted. In this paper, the performance of grid-connected inverter during islanding detection routine test is analyzed with sinusoidal and marginally distorted grid voltage. The results presented in this paper show that grid background harmonics may have significant impacts on inverter control and islanding detection algorithms.