Active islanding detection using high frequency signal injection

Islanding detection is of great importance for reliable operation of smart grids. Islanding detection methods can be classified into three different groups: active, passive and communication based methods. Active methods inject a disturbing signal (typically a voltage) and analyze the system response (typically in the current). These techniques have a low non-detection zone but present the inconvenience inherent to injecting a disturbing signal. Passive methods monitor the grid condition from the grid variables. These techniques are easy to implement, but present a large non-detection zone. Communications methods have the inconvenient of relying on communications, currently being of limited use. This paper proposes a new active islanding detection method, based on measurement of the grid high frequency impedance by means of the injection of a high frequency voltage. Advantages of the method are almost negligible adverse effects due to the injected high frequency voltage and accurate and fast islanding detection -in the rage of few ms-. Furthermore, the estimated high frequency impedance can be used for adaptive control of the power converter.1