METHOD FOR DETECTING FREQUENCY FLUCTUATION OCCURRING IN ELECTRIC POWER SYSTEM, METHOD FOR MEASURING FREQUENCY DEVIATION IN ELECTRIC POWER SYSTEM, AND METHOD FOR MEASURING ELECTRIC POWER SYSTEM FREQUENCY

摘要

PROBLEM TO BE SOLVED: To provide a method for measuring frequency fluctuation and its deviation in an electric power system with high accuracy in an earlier stage than before. ;SOLUTION: Instantaneous voltage values of an electric power system are measured at sampling time points for a predetermined sampling time length Ts. Then, recursive discrete Fouriertransformation is performed based on the instantaneous voltage values to find recursive voltage phasors. Frequency components about twice as high as the fundamental frequency are removed from the voltage phasors by using a filter. Phase deviation of phase components (ϕl, r) at a certain sampling time point from phase components (ϕl, r-l or ϕl, r+l) at a sampling time point immediately before or after the sampling time point is calculated from the voltage phasors from which the frequency components about twice as high as the fundamental frequency are removed. A time point when the phase deviation is produced is detected as the occurrence of frequency fluctuation. A frequency deviation Δf at a certain sampling time point is measured based on the phase deviation.;COPYRIGHT: (C)2004,JPO