US5420495A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Transmission line power flow controller
Assignee: Electric Power Research Institute
•
Filing: 1993-04-19
•
Granted: 1995-05-30
•
Expires: 2013-04-19
Abstract
Abstract A transmission line power flow control system and method selectively reverses power flow direction and controls power flow level over a transmission line. A capacitor having a variable capacitive impedance is selectively inserted in series with the line. The capacitor has a maximum capacitive impedance magnitude which exceeds the magnitude of the inductive impedance of the transmission line. A switching device in parallel with the capacitor inserts and removes the capacitor from the line. The capacitor maybe inserted and removed in a stepwise fashion using several modules, or in a gradual fashion by using inductors in series with the modular switching devices. In response to measurements of power flow parameters, such as line current and line to ground voltages, a controller controls the switching device(s) to selectively vary the net impedance of the transmission line to control the direction and magnitude of power flow therethrough.
Inventors
- 👤 Narain G. Hingorani
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 21:31
CPC Classifications
G; G05; G05F; G05F1/00; G05F1/66
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
217 words
A power flow control system to control the direction of power flow on a transmission line, comprising: a capacitor; a switching device to selectively couple said capacitor to said transmission line; a sensor for monitoring current flowing through said transmission line; and a controller responsive to said sensor to actuate said switching device, said controller including a line current limiter to identify line current on said transmission line above a specified maximum current magnitude limit, a deadband control device responsive to said sensor to establish a deadband range of impedance values and an operative range of impedance values for said transmission line, said operative range of impedance values including negative reactance impedance values and positive reactance impedance values, said line current limiter and said deadband control device generating output signals that are applied to said switching device such that said switching device selectively couples said capacitor to said transmission line to maintain said line current on said transmission line below said specified maximum current magnitude limit, and to maintain said transmission line impedance within said operative range of impedance values and outside of said deadband range of impedance values, and thereby vary said capacitor's reactive power compensation to said transmission line in such a manner as to control the direction of power flow on said transmission line.
Claim 2
Dependent Claim
217 words
A power flow control system to control the direction of power flow on a transmission line, comprising: a capacitor; a switching device to selectively couple said capacitor to said transmission line; a sensor for monitoring current flowing through said transmission line; and a controller responsive to said sensor to actuate said switching device, said controller including a line current limiter to identify line current on said transmission line above a specified maximum current magnitude limit, a deadband control device responsive to said sensor to establish a deadband range of impedance values and an operative range of impedance values for said transmission line, said operative range of impedance values including negative reactance impedance values and positive reactance impedance values, said line current limiter and said deadband control device generating output signals that are applied to said switching device such that said switching device selectively couples said capacitor to said transmission line to maintain said line current on said transmission line below said specified maximum current magnitude limit, and to maintain said transmission line impedance within said operative range of impedance values and outside of said deadband range of impedance values, and thereby vary said capacitor's reactive power compensation to said transmission line in such a manner as to control the direction of power flow on said transmission line.
Claim 3
Dependent Claim
58 words
The power flow control system of claim 1 wherein: said capacitor forms a portion of a plurality of capacitor modules; and said switching device forms a portion of a plurality of switching modules, each of said switching modules of said plurality of switching modules being connected in parallel to a corresponding capacitor of said plurality of capacitor modules.
Claim 4
Dependent Claim
26 words
The power flow control system of claim 2 further including one or more inductors in series with one or more of said plurality of switching modules.
Claim 5
Independent Claim
193 words
A method of controlling the direction of power flow on a transmission line, comprising the steps of: sensing current flow through a transmission line to establish a sensed current signal; comparing said sensed current signal to a specified maximum current magnitude limit and generating a maximum current control signal to maintain said current flow through said transmission line below said maximum current magnitude limit; comparing the impedance of said transmission line with a deadband range of impedance values and an operative range of impedance values for said transmission line, said operative range of impedance values including positive reactance impedance values and negative reactance impedance values, said comparing step including the step of generating a deadband control signal to maintain said transmission line impedance within said operative range of impedance values and outside of said deadband range of impedance values; and applying said maximum current control signal and said deadband control signal to a switching device that selectively connects a capacitor to said transmission line so as to vary said capacitor's reactive power compensation to said transmission line in such a manner as to control the direction of power flow on said transmission line.
Claim 6
Independent Claim
193 words
A method of controlling the direction of power flow on a transmission line, comprising the steps of: sensing current flow through a transmission line to establish a sensed current signal; comparing said sensed current signal to a specified maximum current magnitude limit and generating a maximum current control signal to maintain said current flow through said transmission line below said maximum current magnitude limit; comparing the impedance of said transmission line with a deadband range of impedance values and an operative range of impedance values for said transmission line, said operative range of impedance values including positive reactance impedance values and negative reactance impedance values, said comparing step including the step of generating a deadband control signal to maintain said transmission line impedance within said operative range of impedance values and outside of said deadband range of impedance values; and applying said maximum current control signal and said deadband control signal to a switching device that selectively connects a capacitor to said transmission line so as to vary said capacitor's reactive power compensation to said transmission line in such a manner as to control the direction of power flow on said transmission line.
Claim 7
Dependent Claim
42 words
The method of claim 4 further comprising the steps of: applying said maximum current control signal and said deadband control signal to a plurality of switching modules, each of said switching modules including a switching device connected in parallel with a capacitor.
References Cited (Backward Citations)
US3538352A
Cited
US3544734A
Cited
US3835364A
Cited
US3828281A
Cited
US4121271A
Cited
US4697132A
Cited
US4607243A
Cited
US4728887A
Cited
US4806855A
Cited
US4814559A
Cited
US4792887A
Cited
US4933798A
Cited
US4963845A
Cited
US5227713A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1998-05-29 | 1998-11-28 | 1999-05-30 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2002-05-29 | 2002-11-28 | 2003-05-30 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2006-05-29 | 2006-11-28 | 2007-05-30 | $7700.00 | Window Closed / Lapsed |