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WO2005119393A1 - Système hybride ca/cc destiné à une alimentation - Google Patents

Système hybride ca/cc destiné à une alimentation Download PDF

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Publication number
WO2005119393A1
WO2005119393A1 PCT/US2004/016198 US2004016198W WO2005119393A1 WO 2005119393 A1 WO2005119393 A1 WO 2005119393A1 US 2004016198 W US2004016198 W US 2004016198W WO 2005119393 A1 WO2005119393 A1 WO 2005119393A1
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WO
WIPO (PCT)
Prior art keywords
current
terminal equipment
associated terminal
conductor
conductors
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/US2004/016198
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English (en)
Inventor
Lionel O. Barthold
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Individual
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Individual
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Publication date
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Priority to PCT/US2004/016198 priority Critical patent/WO2005119393A1/fr
Publication of WO2005119393A1 publication Critical patent/WO2005119393A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for AC mains or AC distribution networks
    • H02J3/36—Arrangements for transfer of electric power between AC networks via a high-tension DC link
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/60—Arrangements for transfer of electric power between AC networks or generators via a high voltage DC link [HVCD]

Definitions

  • HVDC high voltage direct current
  • HVDC The economic break-even distance varies greatly from one situation to another but may be in the order of 500 to 800 kM for overhead and one tenth that for underground or under water cables.
  • HVDC is also more efficient in that it uses the insulating strength of the line or cable continuously rather than only during crest voltage as with AC.
  • continuous DC voltage can be at least 2 times the rms AC voltage, power transfer being increased by the same ratio.
  • the increase in DC voltage can be even greater than that since HVDC systems do not require the same additional margin for over- voltages which occur at switching.
  • the resistance of conductors is also slightly lower for DC current inasmuch as electric fields associated with power frequency AC current forces the current distribution to favor the outer periphery of a conductor. With DC or very low frequency AC, the current distribution is more uniform so the electrical resistance is less.
  • the above intrinsic characteristics can result in an HVDC conductor transmitting on the order of 60% more power than the same conductor and same insulation in an AC system.
  • the power which flows in an AC line may fall far short of it's intrinsic thermal capability, being limited by broader system concerns such as stability, voltage control, reactive power transport, and the fact that actual flow is determined by the system context rather than by controls.
  • HVDC has historically and naturally evolved around a transmission system which uses one conductor for positive voltage and current and another for negative voltage and the equal and opposite return current. This is referred to as bi-pole transmission.
  • Each pole, positive and negative, is equipped with its own mono-pole bridge.
  • the thyrister configuration within a conventional bridge is shown in FIG. 2 A. Under normal operating conditions all of the return current is in the second pole, none in the ground.
  • Some lines have been built with one pole only, in which all return current flows in the ground or a metallic ground wire.
  • the invention comprises a system and method which causes three or more conductors to operate under full DC Voltage while controlling current to vary with time in such fashion as to assure that the net power transfer on each conductor is the same as would be carried were that conductor part of a bipolar system.
  • total transmitted power increases proportionately with the number of conductors used.
  • This invention features a method of transmitting power though a transmission system comprising three or more conductors and associated terminal equipment, all subject to a DC voltage, wherein each conductor and its associated terminal equipment has a nominal thermal limit to its current-carrying capacity.
  • the method comprises transmitting current over one or more of the conductors and each such conductor's associated terminal equipment at a level which may be temporarily above the nominal thermally-limited current- carrying capacity ol each con ⁇ uctor ana its associated terminal equipment, and at an essentially constant voltage, returning the transmitted current through the remaining conductors and their associated terminal equipment, wherein the total transmitted and return currents are nominally equal, and periodically altering the current level among the conductors and their associated terminal equipment so as to rotate higher and lower levels of current among the conductors and their associated terminal equipment, such that, over time, the resistance heating of none of the conductors and none of the associated terminal equipment exceeds its thermal limit.
  • Each of the conductors and its associated terminal equipment may transmit current above thermal limit for a time which is nominally less than the thermal time-constant of either the conductor or its associated terminal equipment so as to prevent overheating within the period of rotation of high and low currents.
  • Each conductor and its associated terminal equipment may carry a high level current for a fraction of time equal to the ratio of that conductor to the total number of conductors or conductor groups and a lower level of current for a fraction of time substantially equal to 1 minus that fraction.
  • the polarity of the essentially constant DC voltage and time-varying current in each conductor and its associated terminal equipment may be systematically and simultaneously reversed in order to maintain an essentially continuous power flow in the same direction.
  • the time- varying current flow in each conductor and associated terminal equipment may be switched periodically between one or more positive values of transmitted current for a period of time, zero for a second amount of time, and one or more negative values of return current for a third amount of time.
  • the first and third amounts of time may be approximately equal, and the second may be shorter than the first and third amounts of time and long enough to accommodate switching of pole pola ⁇ ty.
  • the time- varying current may be interrupted briefly prior to changing direction. For any conductor and its associated terminal equipment the average of the square of each level of current multiplied by the time it is carried may be no more than the product of the sum of said time periods and the square of that continuous DC current which could be carried without exceeding the thermal limit of that conductor or its associated terminal equipment.
  • the magnitude of current transmitted and returned in each conductor and its associated terminal equipment may be controlled to be in the form of a low frequency AC sinusoid while the voltage is controlled by means of anti-parallel rectifier and inverter devices to have an essentially constant DC value, periodically reversed in polarity, thus creating a hybrid AC-DC system for transmission of electric power.
  • the power transmission method may further comprise means for converting AC to DC before transmission, and converting DC to AC after transmission.
  • the switching may be accomplished using a series of mono-pole converters equal to the number of conductors, or a cyclo-converter configuration with valve clusters equal to the number of conductors. There may be one such mono-pole converter for each conductor, or one cyclo-converter with one valve cluster for each conductor.
  • the rectifying and inverting valve of mono- converters or cyclo- converter configurations may comprise two thyristers connected in anti-parallel.
  • the switching may be accomplished such that the reversals of current occur at different times on each conductor and its associated terminal equipment.
  • the interruption of current may occur at a time of its minimum magnitude and, further, power transfer on that conductor and associated terminal equipment is interrupted for a period of time very short compared to the period of rotation of current maximum among all conductors and their associated terminal equipment.
  • the switching may be accomplished such that the current in each conductor and its associated terminal equipment increases in a step-wise manner, and decreases in a step-wise manner.
  • Conductors consisting of solid insulation may be reversed in polarity frequently enough to prevent migration of free charge.
  • the build-up of pollution on exposed insulation may be inhibited by periodic reversal of polarity, thereby allowing the use of AC insulators for DC voltage.
  • Equipment which converts AC current to DC and inverts DC current to AC may be used for the conductors and associated terminal equipment, while taking full advantage of the insulation capability and thermal limits of each.
  • This invention also features a system for transmitting power by means of DC voltage, though a transmission system comprising three or more conductors and associated terminal equipment, wherein each conductor and its associated terminal equipment has a nominal thermal limit to its current-carrying capacity.
  • the system includes means for transmitting time- varying current though one or more of the conductors and each such conductor's associated terminal equipment at a level which may be temporarily above the nominal thermally-limited current- carrying capacity of each conductor and its associated terminal equipment, and at essentially constant voltage, means for returning the transmitted current though the remaining conductors and their associated terminal equipment, wherein the total transmitted and return currents are nominally equal, and means for periodically changing the current level in the conductors so as to rotate the higher level current among the conductors and their associated terminal equipment such that, over time, the resistance heating of the conductors and associated terminal equipment does not exceed the thermal limits of any conductor or its associated terminal equipment.
  • FIG. 1 is a schematic diagram of a rectifier or inverter terminal for the invention
  • FIG. 2A is a schematic diagram of a prior art single thyrister valve element
  • FIG. 2B is a schematic diagram of two thyrister valve elements in anti parallel to permit simultaneous reversal of voltage and current, for use in the invention
  • FIG. 3 illustrates examples ofthe current and voltage cycling ofthe preferred embodiment ofthe invention for a three-conductor embodiment.
  • the invention would be embodied by constructing or operating DC transmission line having more than two active conductors and by using a bridge configuration capable of producing a reversing DC voltage and sinusoidal or quasi-sinusoidal low frequency AC current.
  • the preferred equipment used in the invention comprises an array of mono-pole bridge elements, as shown in FIG. 1, wherein each serves a separate conductor in an n-conductor transmission line, where n can be any number greater than 2.
  • n can be any number greater than 2.
  • the invention consists, in part, of causing the current in each pole, under full DC voltage, to vary regularly and systematically with time such that (a) at any given time the sum of positive and negative currents in all poles is zero, (b) the sum ofthe square of current during any interval times the length of that interval is equal to the product of that continuous current which corresponds to thermal limits times the sum of all time intervals and (c) the reversal of polarity in any pole occurs when other poles sustain a high level of current.
  • a sinusoidal current or stepped approximation to a sinusoidal current is a special case meeting those conditions.
  • FIG. 3 illustrates two preferred current modulation patterns for the invention.
  • One modulation is sinusoidal, and the other is a stepped modulation that is essentially sinusoidal, hi each case, at any given time the transmitted and return currents are essentially equal.
  • the thyrite element in each preferred valve being more sensitive to instantaneous than rms current.
  • the thyrite element in valves would have to be rated for a current 2 higher than for the case where the same power is transmitted by continuous DC current.
  • DC voltage applied to each pole must be reversed at the same time its current is reversed.
  • the thyrister elements in each valve must be doubled, each pair being connected in anti-parallel as shown in FIG. 2B.
  • Other components of a valve assembly e.g.
  • grading resisters, damping circuits, and cooling system could be common to both thyristers.
  • HVDC circuits both overhead and underground, are normally capable of reversing power flow by reversals of voltage. That reversal cannot be achieved in any less than the order of 100 milliseconds for overhead lines and longer for underground cables.
  • the invention provides a convenient interval, at minimum power flow during which the current in each pole can be set to zero and the polarity reversed. Inasmuch as the frequency can be very low, e.g.
  • loss of one pole reduces capacity to two thirds, thus providing a 33% increase in first contingency power transfer capacity. If a metallic ground return were added to the three pole conductors, redundancy would be further increased in that transfer would drop to 2/3 with one pole out of service and down to 1/3 with two of three poles out of service. Essentially the same economic arguments apply to underground or submarine cable systems once HVDC has been justified. For example, many major cable circuits are forced to divide total capacity between two bi-pole circuits in order to accommodate the loss of one pole. Even greater reliability can be achieved by the invention if the same capacity is supplied on three circuits; again affording 33% more power with one pole out that in the double bi-pole scheme.
  • both the ratio of post- conversion to pre-conversion power and the cost of new, parallel lines are critical and may limit application to lines or cables which, at present, are able to carry only a small fraction of their AC thermal capability or where the only alternative to uprating by HVDC conversion involves new generating capacity.
  • the tri-pole scheme periodically reverses voltage, it will very likely inhibit accumulation of contaminating particles just as conventional AC does, thereby eliminating the need for specially-designed insulators .
  • Conversion of existing AC underground or submarine systems follows somewhat the same arguments, though with additional considerations.
  • Most presently installed solid insulation cables, for example cannot be used for HVDC because over a long period of time at one polarity, free charge migrates within the insulation and distorts the original voltage gradient.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Rectifiers (AREA)

Abstract

L'invention concerne l'application de courant systématique et à variation temporelle dans un nombre quelconque de conducteurs d'émission, la tension sur chacun de ceux-ci restant, en même temps, à un niveau sensiblement constant mais présentant une polarité inversée périodiquement. Des variations de courant, du courant élevé au courant faible et du courant positif au courant négatif, sont synchronisées de manière à être coordonnées avec la constante temporelle thermique du conducteur ou du câble. Le courant est interrompu sur chaque conducteur pendant un court moment autour d'une valeur zéro, de manière à pouvoir inverser la tension. L'invention concerne également la utilisation thermique totale de chaque conducteur dans le système et le bénéfice simultané tiré de la tension CC continue.
PCT/US2004/016198 2004-05-21 2004-05-21 Système hybride ca/cc destiné à une alimentation Ceased WO2005119393A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
PCT/US2004/016198 WO2005119393A1 (fr) 2004-05-21 2004-05-21 Système hybride ca/cc destiné à une alimentation

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/US2004/016198 WO2005119393A1 (fr) 2004-05-21 2004-05-21 Système hybride ca/cc destiné à une alimentation

Publications (1)

Publication Number Publication Date
WO2005119393A1 true WO2005119393A1 (fr) 2005-12-15

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN109586279A (zh) * 2018-11-20 2019-04-05 国网新疆电力有限公司经济技术研究院 一种互联电网规划方法
CN116111630A (zh) * 2023-04-10 2023-05-12 国网浙江省电力有限公司电力科学研究院 一种输电线路增容方法

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3581152A (en) * 1970-03-16 1971-05-25 Lloyd F Hunt Round protection and detecting for high voltage dc transmission system
US5420495A (en) * 1993-04-19 1995-05-30 Electric Power Research Institute, Inc. Transmission line power flow controller
US6255806B1 (en) * 1998-03-23 2001-07-03 Abb Ab Supply device for power supply to an electronic unit in a semiconductor valve in a shunt-connected thyristor-switched capacitor
US6552598B2 (en) * 2001-07-20 2003-04-22 Vitaly Gelman Semiconductor high voltage electrical energy transmission switching system and method

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3581152A (en) * 1970-03-16 1971-05-25 Lloyd F Hunt Round protection and detecting for high voltage dc transmission system
US5420495A (en) * 1993-04-19 1995-05-30 Electric Power Research Institute, Inc. Transmission line power flow controller
US6255806B1 (en) * 1998-03-23 2001-07-03 Abb Ab Supply device for power supply to an electronic unit in a semiconductor valve in a shunt-connected thyristor-switched capacitor
US6552598B2 (en) * 2001-07-20 2003-04-22 Vitaly Gelman Semiconductor high voltage electrical energy transmission switching system and method

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN109586279A (zh) * 2018-11-20 2019-04-05 国网新疆电力有限公司经济技术研究院 一种互联电网规划方法
CN109586279B (zh) * 2018-11-20 2022-03-25 国网新疆电力有限公司经济技术研究院 一种互联电网规划方法
CN116111630A (zh) * 2023-04-10 2023-05-12 国网浙江省电力有限公司电力科学研究院 一种输电线路增容方法
CN116111630B (zh) * 2023-04-10 2023-09-08 国网浙江省电力有限公司电力科学研究院 一种输电线路增容方法

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