Improved type positive feedback active frequency deviation island detection method

The invention discloses an improved type positive feedback active frequency deviation island detection method, comprising the following steps of: detecting a current frequency of a power grid public point; comparing the current frequency with a last-time frequency to obtain frequency change delta f of the power grid public point; calculating frequency disturbance quantity cf according to a formula: cf=cf'0+k delta f, wherein the cf'0=sign(delta f)*cf0; when the delta f is more than or equal to 0, sign(delta f)=1; when the delta f is less than 0, sign(delta f)=-1; the cf0 is an initial disturbance quantity and the k is feedback gain; and judging whether the frequency disturbance quantity exceeds a frequency threshold value range or not, if so, generating an island on a power grid.