초록 ▼

As a variation of the non-orthogonal filter, a phasor estimate is computed by using an N-point window. An aspect of the sub-window cosine filter is to repeat the basic cosine filter for only selected points of the window. In the end, a least-squares fit is used to obtain an estimate for the phasors

As a variation of the non-orthogonal filter, a phasor estimate is computed by using an N-point window. An aspect of the sub-window cosine filter is to repeat the basic cosine filter for only selected points of the window. In the end, a least-squares fit is used to obtain an estimate for the phasors components. Previous cosine techniques use a data window whose length is greater than 1 cycle while the present invention requires only 1 cycle.

대표청구항 ▼

[ We claim:] [1.] A method for deriving a phasor representation of a current or voltage waveform on a power line, wherein said waveform includes a decaying DC component, comprising the steps of:measuring time-domain samples (v(k), i(k)) of said waveform;computing, on the basis of said samples, a pha

[ We claim:] [1.] A method for deriving a phasor representation of a current or voltage waveform on a power line, wherein said waveform includes a decaying DC component, comprising the steps of:measuring time-domain samples (v(k), i(k)) of said waveform;computing, on the basis of said samples, a phasor representation of said waveform, said phasor representation being computed on the basis of a cosine filtering process comprising steps S1 through S5, as follows:(S1) applying an N-point cosine filter to a window of data points x(0), x(1), . . . x(N-1), wherein the data points comprise measured and digitized current and/or voltage samples;(S2) applying an N/2-point cosine filter to the same window of data points, but using only odd-numbered points x(0), x(2), x(4), etc.;(S3) applying an N/4-point cosine filter to the same window of data points, using only a subset of the data points used in step S2;(S4) applying an N/8-point cosine filter to the same window of data points, using a subset of the data points used in step S3; and(S5) estimating the phasor; andperforming a prescribed power system or protective relaying function using said phasor.