A novel anti-islanding method using positive feedback reactive power variation.

This paper proposes a reactive power variation method based on positive feedback to improve islanding detection for distributed generation. The proposed strategy has a simple structure. The first part involves injecting a constant reactive power and the second part involves injecting a continuously increasing reactive power with positive feedback. Under the islanding condition, the first part serves to initially activate positive feedback by shifting the point of common coupling frequency into a certain operating point. Then the second part plays an important role in accelerating the frequency shift into the over/under threshold level direction. This method does not have a non-detection zone due to the combination of the two parts, and it has good performance regardless of the load conditions. The performance of the proposed method is verified through experiments in a 1.7 kW system, where the detection time is 53 ms with an over-threshold value of 60.5 Hz and 150 ms with an under-threshold value of 57 Hz. [ABSTRACT FROM AUTHOR]