Other

Chubu Electric Power Company, Inc.

Mitsubishi Denki Kabushiki Kaisha

Nissin Electric Co., Ltd.

Isao Koda

Shoji Nishimura

Masakazu Tsukamoto

Yasuyuki Natsuda

Yoshifumi Minowa

Tadahiro Gouda

Toshihiko Shikata

Toshihiro Nakamura

Katsuhiko Uno

Yasuhiro Fuwa

Hirotaka Ono

Taizo Hasegawa

Hideharu Oshida

Hideki Fujita

Toshiharu Narita

A harmonic injection point a is set on a power line extending downstream from a harmonic measuring point b in an electric power system. The currents of interharmonics are injected to the harmonic injection point a by a current injection device. The frequencies of the interharmonics are located on both sides of the frequency of an n-th targeted harmonic in frequency spectrum and each of the frequencies is a nonintegral multiple of the frequency of a fundamental wave of an electric power transmitted by the electric power system. The current values and voltage values of the interharmonics at the harmonic measuring point are detected to thereby obtain admittance values of an equivalent circuit of a power line extending upstream from the harmonic measuring point b when the interharmonics flow therethrough. An admittance value of the equivalent circuit of the power line when the targeted harmonic flows therethrough is determined by interpolating the admittance values for the interharmonics. Measurement is made of a harmonic characteristic of the power line extending upstream from the harmonic measuring point b, which is set at a point located upstream from the harmonic injection point a.

Harmonic measuring method and a current injection device for harmonic measurement

Frequencies fx between the measurement harmonic (mth-degree harmonic) and the (m&plusmn;1)th-degree harmonics are determined from an expression of fx&equals;(fs*m)&plusmn;&lcub;(fs/n)*k)&rcub; where n and k are each an integer. Currents of inter-harmonics of the frequencies fx above and below the measurement harmonic are injected into an inject point in a power system in n cycles of the fundamental wave. Voltage at the inject point based on the injected currents and currents at least either upstream or downstream from the inject point are measured. Admittances for the inter-harmonics above and below the measurement harmonic on at least either the upstream or downstream side from the harmonic inject point are calculated from the measurement results. Interpolation processing based on the calculation results is performed, thereby finding and determining an admittance for the measurement harmonic.

Harmonic component measuring method for power system

Single-phase currents at two frequencies f.alpha. and f.beta. (f.alpha.&lt;n.multidot.fs&lt;f.beta.) of non-integral multiples of a system fundamental wave frequency fs sandwiching an targeted harmonic (frequency n.multidot.fs) are injected between two phases of a three-phase power system as interharmonic currents. A frequency analysis of measurement current and measurement voltage of each phase in the system is carried out and a positive-phase-sequence current I1, a positive-phase-sequence voltage V1, a negative-phase-sequence current I2, and a negative-phase-sequence voltage V2 are detected for each of the two frequencies f.alpha. and f.beta. in the system based on injecting of the interharmonic currents. Positive-phase-sequence and negative-phase-sequence admittances Y1 and Y2 or positive-phase-sequence and negative-phase-sequence impedances Z1 and Z2 are found for each of the frequencies f.alpha. and f.beta. in the system as Y1=I1/V1 and Y2=I2/V2 or Z1=V1/I1 and Z2=V2/I2. Interpolation operation is performed for finding positive-phase-sequence and negative-phase-sequence admittances or positive-phase-sequence and negative-phase-sequence impedances for the targeted harmonic in the system from the admittances Y1 and Y2 or the impedances Z1 and Z2 for the frequencies f.alpha. and f.beta..

Harmonic characteristic measuring method and harmonic characteristic

The power system stabilizer is provided at an individual power system to be separated due to an accident cutting off a link line which interconnects a number of power systems to form a large-scale power system. The power systems include power stations such as power plants and transformer substations. A simplified arithmetic processing unit of the stabilizer performs an arithmetic processing by a simple linear equation using an output frequency of a representative power station belonging to the separated power system immediately after the accident has been cleared, so that a total load drop of the separated power system can be assumed. Based on the assumption amount, balance control of demand and supply in the separated system is made.

Power system stabilizer

Growing community of inventors

Aichi, Japan

Isao Koda