A Novel Method for Anti-Islanding Using Reactive Power

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An islanding occurs when the utility grid is removed but distributed sources continuo to operate and provide power to local loads and grid. This can cause a significant risk to safety and equipment. This report present a novel anti-islanding method to prevent an islanding phenomenon. The proposed method changes the reactive power of the load. Therefore the phase difference between output voltage and current is periodically changed within decided value. When the utility-grid is removed, the frequency of output voltage and current will increase or decrease. And the proposed system will detect the change of frequency and shut down the distributed source. While the conventional methods have some difficulties in detecting particular islanding condition such as a small change in loading, the proposed method can detect most conditions. The performance was verified through experiments.