Anti-Islanding for Three-Phase One-Cycle Control Grid Tied Inverter

An active anti-islanding method for three-phase grid-tied inverters is proposed in this paper. The method is based on asymmetric injection of the converter currents at a subharmonic frequency. This method allows an accurate detection of the islanding condition, thus it minimizes the perturbation to the power system. The theoretical analysis have been confirmed by simulation and by experimental tests conducted on a 40-kW one-cycle control grid tied inverter according to the test procedure outlined in the standard IEEE Std. 1547. The experiments have demonstrated negligible perturbation to the power system, with an increase in the total harmonic distortion of the current of less than 0.1% at full load.