Patent ID: 6208945
Filing Date: 2001-03-27
Classification: G01R

Abstract:
A harmonic component measuring method for a power system, for finding an admittance for a measurement harmonic or an equivalent circuit comprising the admittance and a current source in parallel, wherein an mth-degree harmonic of a frequency which is m times (m is an integer) a frequency fs of a fundamental wave in the power system is used as the measurement harmonic, said harmonic component measuring method comprising the steps of:synchronizing currents of inter-harmonics with the measurement harmonic, wherein the currents of inter-harmonics comprises currents of frequencies fx which are non-integral multiples of the fundamental wave above and below the measurement harmonic;finding and determining the frequencies fx of the currents of inter-harmonics between the mth-degree measurement harmonic and (m.+-.1)th-degree harmonics from an expression of fx=(fs*m).+-.{(fs/n)*k)} where n is an integer of 1, 2, . . . , n responsive to measurement accuracy 1/n (0<1/n<1) and k is an integer of 1, 2, . . . , n for frequency setting;injecting the currents of inter-harmonics into a harmonic inject point in the power system in n cycles of the fundamental wave;measuring voltages at the harmonic inject point based on the injected currents of inter-harmonics and measuring currents at least either upstream or downstream from the harmonic inject point in the power system;calculating admittances for the injected currents of inter-harmonics on at least either an upstream or a downstream side from the harmonic inject point from the measurement results; andperforming interpolation processing based on the calculation results to find the admittance for the measurement harmonic on at least either the upstream or the downstream side from the harmonic inject point.