Non-devastating islanding detection for micro-grid based on mathematical statistics

Conventional passive islanding detection methods have disadvantages of non-detection zone (NDZ). Active ones can reduce or eliminate NDZ, but their operation mechanism is forcing the voltage or frequency into the fault range, which is a devastating islanding detection approach. However, the non-devastating islanding method without NDZ is desirable for micro-grid applications. A novel active islanding detection method based on mathematical statistics for three-phase inverter is proposed. In this paper, 0–1 sequence is used to modulate the PWM modulation wave by amplitude adjustment. Then the voltage of point of common coupling (PCC) is sampled and the variance based on mathematics features is calculated in real-time. According to the value of variance, the islanding can be determined. The proposed method not only conquers the disadvantage of the destroy that conventional active islanding detection methods result in to the utility grid, but also detects the islanding effectively when the DG power production match to the load power requirement. And it is quick and effective under the ideal and non-ideal utility grid and the false islanding also can be prevented. Simulation and experiment results verify the correctness and feasibility of the proposed method. This method is suitable for the grid-connected /stand-alone dual-mode micro-grid system.