Patent ID: 9287714
Filing Date: 2016-03-15
CPC Classification: G01R,H02J

Claim Text:
1. A method of detecting island formation in a distributed power system including at least one distributed generator interruptably coupled to a grid through a feeder, the method comprising: using a frequency measurement device to compile a plurality of values of frequency change in the power system, measured over a predetermined time window; using a processor to group the plurality of values of frequency change into a plurality of bins, a first one of the bins representing an expected behavior of power frequency change when the feeder is grid-tied, a second one of the bins representing an expected behavior of power frequency change when the feeder is islanded, and a third one of the bins representing another expected behavior of power frequency change when the feeder is grid-tied; computing a bimodality index for the grouped values of frequency change; using the processor to apply a predetermined decision criterion to the grouped values of frequency change to determine whether the feeder is islanded or grid-tied, wherein the decision criterion comprises determining whether a value of the bimodality index is in the range of between 0 and 10 over more than 75% of the time window; and automatically decoupling the distributed generator from the feeder if the feeder is determined to be islanded.