US4757415A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Power active filter employing positive sequence filtering
Assignee: Westinghouse Electric Corp
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Filing: 1987-03-16
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Granted: 1988-07-12
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Expires: 2007-03-16
Abstract
Abstract A power active filter circuit for an electric power system includes a reference generator for producing a plurality of balanced, constant amplitude, positive sequence, AC reference voltages, each being phase-locked to a corresponding phase voltage of the power system. Error signals are produced by subtracting the reference voltages from their corresponding phase voltages and a plurality of correction signals, which are proportional to the error signals, are combined with the phase voltages to produce a plurality of output voltages having substantially only a fundamental component.
Inventors
- 👤 Geoffrey M. Smith
- 👤 Eric J. Stacey
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 22:51
CPC Classifications
H; H02; H02J; H02J3/00; H02J3/01; H02M; H02M1/00; H02M1/14; H02M1/15; Y; Y02; Y02E; Y02E40/00; Y02E40/20
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
190 words
A power active filter circuit for an electric power system comprising: means for generating a plurality of balanced, constant amplitude positive sequence reference voltages, each of said reference voltages being phase locked to a corresponding one of a plurality of phase voltages in an electric power system; means for producing a plurality of error signals, each of said error signals being proportional to the difference between one of said AC reference voltages and the corresponding one of said phase voltages; means for creating a plurality of pulse width modulated correction signals, each of said correction signals being proportional to one of said error signals; wherein said means for creating a plurality of correction signals includes a plurality of comparators, each of said comparators being connected to receive one of said error signals and a triangular wave and to produce one of said pulse width modulated correction signals representative of the relative amplitudes of the received error signal and triangular wave; and means for combining each of said correction signals with a corresponding one of said phase voltages, thereby producing a plurality of output voltages having substantially only a fundamental component.
Claim 2
Dependent Claim
190 words
A power active filter circuit for an electric power system comprising: means for generating a plurality of balanced, constant amplitude positive sequence reference voltages, each of said reference voltages being phase locked to a corresponding one of a plurality of phase voltages in an electric power system; means for producing a plurality of error signals, each of said error signals being proportional to the difference between one of said AC reference voltages and the corresponding one of said phase voltages; means for creating a plurality of pulse width modulated correction signals, each of said correction signals being proportional to one of said error signals; wherein said means for creating a plurality of correction signals includes a plurality of comparators, each of said comparators being connected to receive one of said error signals and a triangular wave and to produce one of said pulse width modulated correction signals representative of the relative amplitudes of the received error signal and triangular wave; and means for combining each of said correction signals with a corresponding one of said phase voltages, thereby producing a plurality of output voltages having substantially only a fundamental component.
Claim 3
Dependent Claim
145 words
A circuit as recited in claim 1, wherein: said means for generating said AC reference voltages comprises a sine wave synthesizer for synthesizing said plurality of balanced, constant amplitude AC reference voltages in response to an oscillating signal; a multiphase phase locked loop having inputs for receiving said AC reference voltages and said phase voltages, said multiphase phase locked loop producing a control signal representative of the sum of a plurality of quantities each of said quantities being equal to one of said phase voltages multiplied by the difference between a non-corresponding two of said AC reference voltages; and means for creating said oscillating signal in response to said control signal; and wherein said means for creating said oscillating signal comprises an integrator for integrating said control signal; and a voltage controlled oscillator for producing said oscillating signal in response to said integrated control signal.
Claim 4
Dependent Claim
142 words
A circuit as recited in claim 1, wherein said means for combining comprises: a plurality of bridge networks of controllable switches, each of said bridge networks including a pair of DC input terminals and a pair of AC output terminals; a DC power source connected across each of said pairs of DC input terminals; a plurality of branch circuits each including a capacitor and an inductor electrically connected in series, each of said branch circuits being connected across said one of said pairs of AC output terminals; a plurality of transformers, each of said transformers having a first winding connected across one of said capacitors and a second winding connected in series with one phase of said electric power system; and a plurality of drive circuits for controlling the operation of said controllable switches in response to said pulse width modulated waves.
Claim 5
Independent Claim
227 words
A method of filtering a plurality of phase voltages of a multiple phase electric power system, said method comprising the steps of: synthesizing a plurality of balanced, constant amplitude positive sequence AC reference voltages in response to an oscillating signal, each of said reference voltages being phase locked to a corresponding one of a plurality of phase voltages of a multiple phase electric power system; passing said AC reference voltages and said phase voltages into a multiple phase phase-locked loop to produce a control signal representative of the sum of a plurality of quantities, each of said quantities being equal to one of said phase voltages multiplied by the difference between a non-corresponding two of said AC reference voltages; integrating the control signal; producing said oscillating signal in response to the integrated control signal; producing a plurality of error signals, each of said error signals being proportional to the difference between one of said AC reference voltages and a corresponding one of said phase voltages; comparing each one of said error signals with a triangular wave to produce a plurality of pulse width modulated correction signals, each of said correction signals being proportional to one of said error signals; and combining each of said correction signals with a corresponding one of said phase voltages, thereby producing a plurality of output voltages having substantially only a fundamental component.
Claim 6
Independent Claim
227 words
A method of filtering a plurality of phase voltages of a multiple phase electric power system, said method comprising the steps of: synthesizing a plurality of balanced, constant amplitude positive sequence AC reference voltages in response to an oscillating signal, each of said reference voltages being phase locked to a corresponding one of a plurality of phase voltages of a multiple phase electric power system; passing said AC reference voltages and said phase voltages into a multiple phase phase-locked loop to produce a control signal representative of the sum of a plurality of quantities, each of said quantities being equal to one of said phase voltages multiplied by the difference between a non-corresponding two of said AC reference voltages; integrating the control signal; producing said oscillating signal in response to the integrated control signal; producing a plurality of error signals, each of said error signals being proportional to the difference between one of said AC reference voltages and a corresponding one of said phase voltages; comparing each one of said error signals with a triangular wave to produce a plurality of pulse width modulated correction signals, each of said correction signals being proportional to one of said error signals; and combining each of said correction signals with a corresponding one of said phase voltages, thereby producing a plurality of output voltages having substantially only a fundamental component.
Claim 7
Dependent Claim
100 words
The method of claim 4, wherein the combining step comprises the steps of: connecting a DC power source to a pair of DC input terminals on a bridge network of controllable switches; connecting a branch circuit comprising the series connection of a capacitor and an inductor between a pair of AC output terminals on said bridge network; connecting a first winding of a transformer in parallel with said capacitor and connecting a second winding of said transformer in series with one phase of said electric power system; and operating said controllable switches in response to said pulse width modulated wave.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1991-07-12 | 1992-01-11 | 1992-07-12 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1995-07-12 | 1996-01-11 | 1996-07-12 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1999-07-12 | 2000-01-11 | 2000-07-12 | $7700.00 | Window Closed / Lapsed |