his paper presents an overview of power system islanding and islanding detection techniques.

Islanding detection methods for distributed resources are reviewed. Special emphasis is put on some of the detecting systems based on “active methods” which have been developed in Japan for rotating machine type distributed generations. Then, reduction of the islanding detection sensitivity with multiple distributed generations is discussed. Finally, a new concept of an islanded operation is introduced.

A method of controlling a generator system connected to an electric power system in which the output frequency characteristic of the generator system is measured, a first phase angle and frequency of the measured frequency characteristic is estimated using a first phase locked loop having a first bandwidth, and a second phase angle and frequency of the measured frequency characteristic is estimated using a second phase locked loop having a second bandwidth greater than the first bandwidth.