Novel Islanding Detection Method for Multiple DGs Based on Forced Helmholtz Oscillator

This paper proposes a novel, passive-based anti-islanding method for both inverter and synchronous machine-based distributed generation units. Unfortunately, when the active/reactive power mismatch is near to zero, the majority of passive anti-islanding methods cannot detect the islanding situation. This paper introduces a new islanding detection method based on the chaos theory that can detect the islanding condition with near-zero active power mismatch. The method uses the modified frequency of the point of common coupling link as an input signal of forced Helmholtz oscillator. The obvious change between chaotic and normal motions in the forced Helmholtz oscillator is its main advantage over other oscillators. This change determines the threshold for detection index. The non-islanding transient events, which can cause a significant deviation in the frequency-based input signal of detector, are considered in simulations for two different case studies. These events include different types of faults, load changes, capacitor bank switching, and motor starting. Further, for islanding events, the capability of the proposed islanding detection method is verified by near-to-zero active power mismatches and UL 1741-based load imbalance tests.