EP0483405A1
Expired / Lapsed
EP
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Flicker compensating apparatus for DC arc furnace
Assignee: JFE Engineering Corp
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Filing: 1990-10-31
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Granted: —
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Expires: 2010-10-31
Abstract
Abstract A flicker compensating apparatus for compensating for flickering due to a variation in the reactive power generated from a DC arc furnace (25) connected by an AC/DC converter (23) to an AC power system (21), comprises a current detector (32) for detecting a DC current flowing in the DC arc furnace (25), a controller (33) for determining the phase control angle of a thyristor included in the AC/DC converter (23) in accordance with the difference between the detected DC current and a predetermined reference current, a calculator (41) for calculating reactive power to be generated by the DC arc furnace (25), from the detected DC current, the determined phase control angle, and a no-load DC voltage, a compensator (46) including a reactive load (45) connected via a thyristor (44) to the power system (21), and a controller (42) for controlling the phase control angle of the thyristor (44) of the compensator (46) in accordance with the calculated reactive power, for controlling a current flowing across the reactive load (45), and for permitting the compensator (46) to generate such reactive power as to compensate for a variation in the calculated reactive power.
Inventors
- 👤 Norio C/O Patent & License Department Ao
- 👤 Kazuhiko C/O Patent & License Department Mori
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-02 10:26
CPC Classifications
H; H02; H02J; H02J3/00; H02J3/18; H02J3/1821; H02J3/1835; H02J3/1864; C; C21; C21C; C21C5/00; C21C5/52; C21C5/5229; H05; H05B; H05B7/00; H05B7/02; H05B7/144; Y; Y02; Y02E; Y02E40/00; Y02E40/10; Y02P; Y02P10/00; Y02P10/20; Y02P10/25; Y02P10/32
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
174 words
A flicker compensating apparatus for a DC arc furnace (25) connected via AC/DC converting means (23) to an AC power system (21), comprising flicker compensating means (46) for applying reactive power to the power system (21) and having, for each phase of the AC power system, a reactance (45) for controlling through a switching element (44) a current supplied to a reactive load (45) and a capacitor (47) for serving as a high harmonic filter and improving a power factor, the switching element (44) being a thyristor, characterized by comprising a control circuit for the thyristor (44) which comprises calculating means for detecting and calculating an effective value of reactive power of the DC arc furnace, wherein said calculating means comprises: current detecting means (32) for detecting an instantaneous value of the effective DC current flowing through the AC/DC converting means (23); phase angle control means (33) for controlling a phase control angle of the AC/DC converting means (23); and converting means (36) for obtaining a no-load DC voltage of the AC/DC converting means.
Claim 2
Dependent Claim
104 words
An apparatus according to claim 1, characterized in that said calculating means (41) comprises: means for calculating the reactive power according to a product of a sin value of the phase control angle output from said phase angle control means and the instantaneous value of the DC current detected by said current detecting means; and means for calculating the reactive power according to a product of a sin value of the phase control angle output from said phase angle control means, the instantaneous value of the DC current detected by said current detecting means, and the no-load DC voltage obtained by said converting means.
Claim 3
Dependent Claim
227 words
A flicker compensating apparatus for a DC arc furnace (25) connected via AC/DC converting means (23) to an AC power system (21), comprising flicker compensating means (46) for applying reactive power to the power system (21) and having, for each phase of the AC power system, a reactance (45) for controlling through a switching element (44) a current supplied to a reactive load (45) and a capacitor (47) for serving as a high harmonic filter and improving a power factor, the switching element (44) being a thyristor, characterized by comprising a control circuit for the thyristor (44) which comprises calculating means for detecting and calculating an effective value of reactive power of the DC arc furnace, wherein said calculating means comprises: first calculating circuit (41) comprising current detecting means (32) for detecting an instantaneous value of the effective DC current flowing through the AC/DC converting means (23), phase angle control means (33) for controlling a phase control angle of the AC/DC converting means (23), and converting means (36) for obtaining a no-load DC voltage of the AC/DC converting means; power detecting means (51) for detecting the reactive power of the power system; and means (42) for controlling the switching element (44) based on a difference between the reactive power calculated by said first calculating circuit (41) and the reactive power detected by said power detecting means (51).
Claim 4
Dependent Claim
105 words
An apparatus according to claim 3, characterized in that said first calculating circuit (41) comprises: means for calculating the reactive power according to a product of a sin value of the phase control angle output from said phase angle control means and the instantaneous value of the DC current detected by said current detecting means; and means for calculating the reactive power according to a product of a sin value of the phase control angle output from said phase angle control means, the instantaneous value of the DC current detected by said current detecting means, and the no-load DC voltage obtained by said converting means.
Claim 5
Dependent Claim
68 words
A flicker compensating apparatus for a DC arc furnace (25) connected via AC/DC converting means (23) to an AC power system (21), characterized by comprising: means (41) for calculating reactive power generated by the DC arc furnace based on a phase control angle of said AC/DC converting means (23); and means (46) for applying said reactive power calculated by said calculating means (41) to said power system (21).
Claim 6
Dependent Claim
26 words
An apparatus according to claim 5, characterized in that said applying means (46) includes a reactance (45) connected to each phase of said power system (21).
Claim 7
Dependent Claim
56 words
An apparatus according to claim 6, characterized in that said applying means (46) further includes: a thyristor (44) connected between said reactance (45) and each phase of said power system (21); and means (42) for controlling a phase control angle of said thyristor (44) in accordance with said reactive power calculated by said calculating means (41).
Claim 8
Dependent Claim
33 words
An apparatus according to claim 6, characterized by further comprising a capacitor (47) serving as a high harmonic filter and improving a power factor, connected to each phase of said power system (21).
Claim 9
Dependent Claim
101 words
An apparatus according to claim 5, characterized in that said calculating means (41) comprises: means (32) for detecting a DC current flowing through said AC/DC converting means (23); phase angle control means (33) for calculating a phase control angle of said AC/DC converting means (23) based on a difference between said DC current detected by said detecting means (32) and a reference current; and means (41) for calculating reactive power according to a product of a sin value of said phase control angle calculated by said phase angle control means (33) and said DC current detected by said detecting means (32).
Claim 10
Dependent Claim
125 words
An apparatus according to claim 5, characterized in that said calculating means (41) comprises: means (32) for detecting a DC current flowing through said AC/DC converting means (23); phase angle control means (33) for calculating a phase control angle of said AC/DC converting means (23) based on a difference between said DC current detected by said detecting means (32) and a reference current; means (36) for detecting a no-load DC voltage of said power system; and means (41) for calculating reactive power according to a product of a sin value of said phase control angle calculated by said phase angle control means (33), said DC current detected by said current detecting means (32) and the no-load DC voltage detected by said voltage detecting means (36).
References Cited (Backward Citations)
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