WO2014166026A1 - Methods for de-icing transmission lines in bipolar series mtdc system and system thereof - Google Patents

Methods for de-icing transmission lines in bipolar series mtdc system and system thereof Download PDF

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Publication number
WO2014166026A1
WO2014166026A1 PCT/CN2013/073794 CN2013073794W WO2014166026A1 WO 2014166026 A1 WO2014166026 A1 WO 2014166026A1 CN 2013073794 W CN2013073794 W CN 2013073794W WO 2014166026 A1 WO2014166026 A1 WO 2014166026A1
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Prior art keywords
voltage level
terminal
pole
converter
high voltage
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PCT/CN2013/073794
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French (fr)
Inventor
Dawei YAO
Xiaobo Yang
Chunming YUAN
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Abb Technology Ltd.
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Priority to PCT/CN2013/073794 priority Critical patent/WO2014166026A1/en
Publication of WO2014166026A1 publication Critical patent/WO2014166026A1/en

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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02G—INSTALLATION OF ELECTRIC CABLES OR LINES, OR OF COMBINED OPTICAL AND ELECTRIC CABLES OR LINES
    • H02G1/00—Methods or apparatus specially adapted for installing, maintaining, repairing or dismantling electric cables or lines
    • H02G1/02—Methods or apparatus specially adapted for installing, maintaining, repairing or dismantling electric cables or lines for overhead lines or cables
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02G—INSTALLATION OF ELECTRIC CABLES OR LINES, OR OF COMBINED OPTICAL AND ELECTRIC CABLES OR LINES
    • H02G7/00—Overhead installations of electric lines or cables
    • H02G7/16—Devices for removing snow or ice from lines or cables

Definitions

  • the invention relates to the technical field of series MTDC system, and more particularly to methods for de-icing transmission lines in a 3-terminal or 4-termia! bipolar series MTDC system.
  • Ice coating will reduce the mechanical strength and electrical performance of transmission lines, which leads to a reduced reliability of HVDC system.
  • Such problem also occurs in multi-terminal DC (MTDC) system, especially seriously in China.
  • Fig.1 illustrates a 4-terminal bipolar series MTDC system under normal operation according to prior art.
  • the 4-terminal bipolar series MTDC system comprises 4 terminals, such as the first low voltage level terminal R1 , the first high voltage level terminal R2, the second high voltage level terminal I2 and the second low voltage level terminal 11 ; each of which comprises a converter in the positive pole and a converter in the negative pole.
  • two terminals R1 and R2 are operated as rectifiers and the other two terminals I2 and 11 are operated as inverters.
  • the rated parameter of each converter is 400kV/4kA. It is assumed in this part that, AC power generation capacity of terminal R1 and R2 is not influenced by winter.
  • the R1 and R2, and I2 and 11 are respectively connected via low voltage level transmission lines, for example 400kV level; and R2 and 12 are connected via high voltage level transmission lines, for example 800kV level, in particular, all converters are connected in series, and the DC current through such converters is same each other, for example 4kA.
  • (1a ⁇ , 1 b ⁇ , 1c ⁇ and 1d ⁇ ) represent the auxiliary metallic lines functioning as conductors in every terminal.
  • the present invention proposes methods for de-icing transmission lines in a 4-termina! bipolar series MTDC system and system thereof, which are applicable and flexible for de-icing all transmission lines, high voltage level transmission lines or low voltage level transmission iines individually.
  • the present invention provides a method for de-icing all transmission Iines in a bipolar series MTDC system, wherein the method comprises: bypassing each converter of a kind of pole in all terminals and making ail transmission Iines of the kind of pole functioned under metaliic return mode; and reconnecting the converter in parallel with a converter of a contrary pole in the same terminal individually.
  • the present invention provides a method for de-icing low voltage level transmission Iines in a bipolar series MTDC system, wherein the method comprises: bypassing each converter of a kind of pole in all terminals and making all transmission Iines of the kind of pole functioned under metallic return mode; reconnecting the converter in low voltage level terminals in parallel with a converter of a contrary pole in the same terminals individually; and reconnecting the converter in high voltage level terminals in anti-parallel with the low voltage level terminals.
  • the converter (R1-) of a kind of pole in a lowireage level rectifier terminal is operated as rectifier to increase current through the low voltage level transmission lines between the low voltage level rectifier terminal (R1 ) and the high voltage level rectifier terminal (R2).
  • the converter (R2-) of a kind of pole in a high voltage level rectifier terminal is operated as inverter to decrease current through the highireage level transmission lines between the high voltage level rectifier terminal (R2) and the high voltage level inverter terminal (12).
  • the converter (12-) of a kind of pole in a high voltage level inverter terminal is operated as rectifier to increase current through the low voltage level transmission lines between a lowiserage level inverter terminal (11 ) and the high voltage level inverter terminai (I2).
  • the converter (11-) of a kind of pole in a low voltage level inverter terminal is operated as inverter.
  • the present invention provides a method for de-icing low voltage level transmission lines in a 4-termial bipolar series MTDC system.
  • the method comprises: on-line splitting the 4-terminai bipolar series MTDC system into two bipolar 2-termina! HVDC systems; bypassing each converter of a kind of pole in all terminals and making low voltage level transmission lines of the kind of pole functioned under metallic return mode; reconnecting the converter in parallel with a converter of a contrary pole in the same terminals individually.
  • the on-line splitting step further comprises: operating the high voltage level rectifier terminal (R2) as inverter terminal and the highréage level inverter terminal (12) as rectifier terminal; connecting metallic return conductors and local earth electrodes of the high voltage level rectifier terminal (R2) and the high voltage level inverter terminal (12) between high voltage transmission line in positive pole and high voltage transmission line in the negative pole to form two return paths and bypassing the high voltage transmission lines; and disconnecting the high voltage transmission lines between the high voltage level rectifier terminal (R2) and the high voltage level inverter terminal (12).
  • the converters in a high voltage level rectifier terminal are operated as inverters and the converters in a high voltage level inverter terminal are operated as rectifiers.
  • the de-icing function on low voltage level transmission lines between the high voltage level terminals and low voltage level terminals is realized without impact on the current through high voltage level transmission lines between the high voltage level terminals.
  • the present invention provides a method for de-icing a single group of low voltage level transmission lines in a 4-termial bipolar series MTDC system, wherein the method comprises: bypassing each converter of a kind of pole in all terminals, and making the transmission lines in the kind of pole functioned under metallic return mode; and reconnecting the converter in the low voltage level terminal in parallel with the converter of contrary pole in the same terminal individually; reconnecting the converter in the high voltage level terminal in anti-parallel with the low voltage level terminal.
  • the conversion mode of the converter of a kind of pole in a low voltage level terminal (R1-) is same to that of the converter of a contrary pole in the same terminal to increase current on the single group of the low voltage level transmission lines; and the conversion mode of the converter of a kind of pole in a high voltage level terminal (R2-) is contrary to that of the converter of a contrary pole in the same terminal to decrease current on the high voltage level transmission lines.
  • the method further comprises: reconnecting each converter of a kind of pole in two terminals which are connected via the other group of low voltage level transmission lines in the kind of pole in parallel with a converter of a contrary pole in the same terminal individualiy; and operating the converter of the kind of pole in the two terminals under a conversion mode which is the same as the conversion mode of the converters of a contrary pole in the same terminal individually.
  • the method further comprises: reconnecting each converter of a kind of pole in the high voltage level terminal and low voltage terminal which are connected via the other group of low voltage level transmission in the kind of pole in series with the series MTDC system; operating the converter of the kind of pole (12-) in the high voltage level terminal (12) under the conversion mode which is contrary to the conversion mode of the converter of a contrary pole in the same terminal; and operating the converter of the kind of pole in the low voltage level terminal (11 -) under the conversion mode which is the same as the conversion mode of the converter of a contrary pole in the same terminal.
  • the method further comprises: reconnecting each converter of a kind of pole in the high voltage level terminal and low voltage level terminal which are connected via the other group of low voltage level transmission line in said kind of pole in series with the series MTDC system; operating the converter of the kind of pole (12-) in the high voltage level terminal (12) under the conversion mode which is the same as the conversion mode of the converter the converter of a contrary pole in the same terminal; and operating the converter of the kind of pole (11-) in the low voltage level terminal (11 ) under the conversion mode which is contrary to the conversion mode of the converter of a contrary pole in the same terminal.
  • the de-icing function on a single group of low voltage level transmission lines in a 4-terminal bipolar series MTDC system is realized without impact on the current through other transmission lines in the 4-terminai bipolar series MTDC system.
  • the kind of pole can be negative pole or positive pole, and the contrary pole is positive pole or negative pole respectively.
  • the present invention provides a method for de-icing high voltage level transmission lines in a 4-termial bipolar series MTDC system, wherein the method comprises: bypassing two high voltage level terminals of the system; and reconnecting the rectifier terminal of the two high voltage level terminals in parallel with the low voltage level rectifier terminal; and reconnecting the inverter terminal of the two high voltage level terminals in parallel with the low voltage level inverter terminal.
  • the de-icing function on high voltage level transmission lines between the high voltage level terminals is realized without impact on the current through low voltage level transmission lines between the high voltage level terminal and low voltage level terminal.
  • Embodiments of the present invention propose methods for de-icing transmission lines in a 4-terminal bipolar series MTDC system and a system thereof, which facilitate the development of series MTDC applications and long distance transmission of power in low temperature area.
  • the methods for de-icing of transmission lines won't cause MTDC system shutdown and temperature rise on undesired transmission lines.
  • Fig.1 illustrates a 4-terminal bipolar series MTDC system under normal operation according to prior art
  • Fig.2a illustrates a configuration of 4-terminal bipolar series MTDC system for de-icing all transmission fines according to an embodiment of the present invention
  • Fig.2b illustrates a configuration of 3-terminal bipolar series MTDC system for de-icing all transmission lines according to an embodiment of the present invention
  • Fig.3a illustrates a configuration of 4-terminal bipolar series MTDC system for de-icing ail low voltage level transmission lines according to an embodiment of the present invention
  • Figs.3b, 3c and 3d together illustrate a configuration of de-icing all low voltage level transmission lines for 4-terminal bipolar series MTDC system according to another embodiment of the present invention
  • Fig.4 illustrates a configuration of 4-terminal bipolar series MTDC system for de-icing a single group of low voltage level transmission lines according to an embodiment of the present invention
  • Fig.5a illustrates a configuration of 4-terminal bipolar series MTDC system for de-icing a single group of low voltage level transmission lines according to another embodiment of the present invention
  • Fig.5b illustrates another configuration of 4-terminal bipolar series MTDC system for de-icing a single group of low voltage level transmission lines according to an embodiment of the present invention
  • Fig.5c illustrates another configuration of 4-terminal bipolar series MTDC system for de-icing a single group of low voltage level transmission lines according to an embodiment of the present invention.
  • Fig.6 illustrates a configuration of 4-terminal bipolar series MTDC system for de-icing high voltage level transmission lines according to an embodiment of the present invention
  • Fig.2a illustrates a configuration of 4-terminal bipolar series MTDC system for de-icing all transmission lines according to an embodiment of the present invention.
  • each converter of a kind of pole (for example the negative pole) in all terminals is bypassed by means of isolators or switches; all corresponding transmission lines are functioned under metallic return mode; and each of bypassed converters is re-connected in parallel with the converter of a contrary pole (for example the positive pole) in the same terminal individually.
  • the converter R1- is connected to the converter R1+ in parallel, and so forth.
  • the method for de-icing all transmission lines in such 4-terminal bipolar series MTDC system is not limited to operate all the converters in negative poles.
  • ail converters in positive pole of each terminal can be bypassed and then reconnected to the corresponding converters in negative pole of the same terminals for de-icing all the transmission lines to achieve the same performance.
  • Fig.2b illustrates a 3-terminal bipolar series MTDC system.
  • the 3-terminal bipolar series MTDC system comprises 3 terminals, such as the first low voltage- level terminal R1 , the first high voltage level terminal R2, and the second low voltage level terminal 11 ; each terminal comprises a converter in the positive pole and a converter in the negative pole.
  • two terminals R1 and R2 are operated as rectifiers and the other terminal !1 is operated as inverter.
  • the rated parameter of rectifier converter is 400kV/4kA and that of inverter converter is 800kV/4kA.
  • the terminals R1 and R2 are respectively connected via low voltage level transmission lines, for example 400kV level; and R2 and 11 are connected via high voltage level transmission lines, for example 800kV level.
  • all converters are connected in series, and the DC current through such converters is same each other, for example 4kA.
  • each converter of a kind of pole for example the negative pole
  • all corresponding transmission lines are functioned under metallic return mode
  • each of bypassed converters is re-connected in parallel with the converter of a contrary pole (for example the positive pole) in the same terminal individually.
  • the converter R1- is connected to the converter R1+ in parallel, and so forth.
  • Fig.3a illustrates a configuration of 4-terminal bipolar series MTDC system for de-icing all low voltage level transmission lines according to an embodiment of the present invention.
  • Fig.3a there are two transmission line groups with 400kV voltage level.
  • One group is 400kV level lines between terminal R1 and terminal R2, the other is 400kV level lines between terminal 11 and terminal I2.
  • the converter R1- in the first low voltage level rectifier terminal is operated as rectifier to increase current through the low voltage level transmission lines between the first low voltage level rectifier terminal (R1 ) and the first high voltage level rectifier terminal (R2), i.e. to inject the additional current to +400kV level lines between R1 and R2.
  • the converter (R2-) in the first high voltage level rectifier terminal is operated as inverter to decrease current through the high voltage level transmission lines between the first high voltage level rectifier terminal (R2) and the second high voltage level inverter terminal (I2), i.e. to absorb additional current from +400kV level lines between R1 and R2 and inject the absorbed current to the related -400kV level lines, which now is operated under metallic return mode.
  • the converter (I2-) in the second high voltage level inverter terminal is operated as rectifier to increase current through the low voltage level transmission lines between a second low voltage level inverter terminal (11 ) and the second high voltage level inverter terminal (I2), i.e. to inject additional current absorbed from -400kV level lines (operated under metallic return mode) between 11 and I2 to the related +400kV level Sines.
  • the converter (11-) in the second low voltage level inverter terminal is operated as inverter, i.e. to absorb the additional current from +400kV level line between M and 12 and inject it to the related -400kV level line (operated under metallic return mode now).
  • Figs.3b, 3c and 3d together illustrate a method for de-icing all low voltage level transmission lines of 4-terminal bipolar series MTDC system according to another embodiment of the present invention.
  • the 4-terminal bipolar series MTDC system can be on-line split into two bipolar 2-terminal DC systems without system shutdown.
  • conversion mode of high voltage level rectifier terminal R2 is changed to inverter and conversion mode of high voltage level inverter terminal 12 is changed to rectifier.
  • metallic return conductors and local earth electrodes of the high voltage level rectifier terminal (R2) and the high voltage level inverter terminal (12) are connected between +800kV transmission line and -800kV transmission line to form two return paths and bypass the ⁇ 800kV level transmission lines; and disconnecting the +800kV and -800kV high voltage transmission lines between the high voltage level rectifier terminal (R2) and the high voltage level inverter terminal (12).
  • terminal R2 is normally located at power generation base, which means local load may be not sufficient to consume all the required power.
  • terminal 12 is normally designed to be at load center, which means there may be no enough power for de-icing.
  • Fig.4 illustrates a configuration of 4-terminal bipolar series MTDC system for de-icing a single group of low voltage level transmission lines according to an embodiment of the present invention.
  • the conversion mode of the converter of the negative pole in a low voltage level terminal (R1-) is operated the same as that of the converter of the positive pole to increase current on the low voltage level transmission lines between the low voltage level terminal (R1 ) and the high voltage level terminal (R2); i.e. to inject the additional current to +400kV level lines between R1 and R2.
  • the conversion mode of the converter of the negative pole in the high voltage level terminal (R2-) is operated contrary to that of the converter of the positive pole to decrease current on the high voltage level transmission lines between high voltage level terminals; i.e. to absorb additional current from +400kV level lines between R1 and R2, and inject the absorbed current to the related -400kV level line (operated under metallic return mode now).
  • Fig.5a illustrates a configuration of 4-terminal bipolar series MTDC system for de-icing a single group of low voltage level transmission lines according to an embodiment of the present invention.
  • the method for de-icing a single group of low voltage level transmission lines between terminal R1 and R2 further comprises: besides bypassing each converter ⁇ 12-, 11-) in two terminals (I2, 11 ) which are connected via the other group of low voltage level transmission lines, the converters (I2-, 11-) of the two terminals are reconnected in parallel with converters (I2+, 11 +) in the same terminal individually.
  • converters (I1 +, 11-) and (I2+, I2-) can be the backup each other.
  • the converted power of each terminal is reduced 50%.
  • Fig.5b illustrates another configuration of 4-terminal bipolar series MTDC system for de-icing a single group of low voltage level transmission lines according to an embodiment of the present invention.
  • the converter 12- and converter 11- is reconnected to the MTDC system in series.
  • the conversion mode of the converter (I2-) in the high voltage level terminal connected to the other group of low voltage level transmission lines is contrary to that of the converter of the positive pole (I2+) in the same terminal I2; and the conversion mode of a converter of negative pole in the low voltage level terminal (11-) connected to the other group of low voltage level transmission lines is the same as that of the converter (11 +) of the positive pole in the same terminal 11.
  • terminal 11 Assuming all converters are operated with rated current, the full power operation of terminal 11 can be ensured by the alternative embodiment. However, terminal 12 and R2 will stop the bulk power delivery to its AC grid.
  • Fig.5c illustrates another configuration of 4-terminal bipolar series MTDC system for de-icing a single group of low voltage level transmission lines according to an embodiment of the present invention.
  • the converter 12- and the converter i1- is reconnected to the MTDC system in series.
  • the conversion mode of a converter (I2-) of the negative pole in the high voltage level terminal (I2) which is connected to the other group of low voltage level transmission lines is the same as that of the converter of the positive pole (I2+) in the same terminal (12); and the conversion mode of the converter (11-) of the negative pole in the low voltage level terminal (11 ) which is connected to the other group of low voltage level transmission lines is contrary to that of the converter of the positive pole (11+) in the same terminal.
  • terminal 12 Assuming all converters are operated with rated current, the fuil power operation of terminal 12 can be ensured by this alternative implementation. However, terminal 1 and R2 will stop the bulk power delivery to its AC grid.
  • the de-icing function on a single group of low voltage level transmission lines in a 4-terminai bipolar series MTDC system is realized without impact on the current through other transmission lines in the 4-terminal bipolar series MTDC system.
  • Fig .6 illustrates a configuration of 4-terminal bipolar series MTDC system for de-icing high voltage level transmission lines according to an embodiment of the present invention.
  • the method for de-icing high voltage level transmission lines in a 4-termial bipolar series MTDC system comprises bypassing two high voltage level terminals of the system; and reconnecting the two high voltage level terminals in parallel with low voltage level terminals individually.
  • the present invention also proposes a system, which utilizes above mentioned de-icing method.
  • the proposed de-icing methods will not cause MTDC system shutdown during de-icing of selected transmission lines.

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Abstract

Methods for de-icing transmission lines in a 4-terminal (or 3-terminal) bipolar series MTDC system include: bypassing each converter (R1-, R2-, I2-, I1-) of a kind of pole in all terminals and making all transmission lines of the kind of pole functioned under metallic return mode; and reconnecting the converter in parallel with a converter (R1+, R2+, I2+, I1+) of a contrary pole in the same terminal individually. For de-icing the target transmission lines, the de-icing operation can be realized without impact on other unselected transmission lines. Hence, the methods are more practical and flexible for de-icing implementation on series MTDC system.

Description

METHODS FOR DE-ICING TRANSMISSION LINES IN BIPOLAR SERIES MTDC
SYSTEM AND SYSTEM THEREOF
FIELD OF THE INVENTION The invention relates to the technical field of series MTDC system, and more particularly to methods for de-icing transmission lines in a 3-terminal or 4-termia! bipolar series MTDC system.
BACKGROUND OF THE INVENTION Ice coating will reduce the mechanical strength and electrical performance of transmission lines, which leads to a reduced reliability of HVDC system. Such problem also occurs in multi-terminal DC (MTDC) system, especially seriously in China.
Fig.1 illustrates a 4-terminal bipolar series MTDC system under normal operation according to prior art. As shown in Fig.1 , the 4-terminal bipolar series MTDC system comprises 4 terminals, such as the first low voltage level terminal R1 , the first high voltage level terminal R2, the second high voltage level terminal I2 and the second low voltage level terminal 11 ; each of which comprises a converter in the positive pole and a converter in the negative pole. In this system, two terminals R1 and R2 are operated as rectifiers and the other two terminals I2 and 11 are operated as inverters. For example, the rated parameter of each converter is 400kV/4kA. It is assumed in this part that, AC power generation capacity of terminal R1 and R2 is not influenced by winter. This means that all the converters can be operated under rated power. The R1 and R2, and I2 and 11 are respectively connected via low voltage level transmission lines, for example 400kV level; and R2 and 12 are connected via high voltage level transmission lines, for example 800kV level, in particular, all converters are connected in series, and the DC current through such converters is same each other, for example 4kA. (1a±, 1 b±, 1c± and 1d±) represent the auxiliary metallic lines functioning as conductors in every terminal.
Various de-icing methods for common point-to-point HVDC system have been proposed and also applied in practice. However, those de-icing methods for point-to-point HVDC system cannot be applied directly to series MTDC system. Generally in series MTDC system, transmission lines between terminals (also named converter stations) are designed for different voltage levels. Common de-icing methods may lead to an increased power loss and undesired temperature rise on certain transmission lines for series MTDC system. Even worse, conflict of voltage or current limitations may occur on converters or transmission lines.
Due to the above mentioned problems, methods for de-icing transmission lines in a 4-termial bipolar series MTDC system is proposed in the present invention without system shutdown provision or performance deterioration.
SUMMARY OF THE INVENTION
To overcome the problems mentioned above, the present invention proposes methods for de-icing transmission lines in a 4-termina! bipolar series MTDC system and system thereof, which are applicable and flexible for de-icing all transmission lines, high voltage level transmission lines or low voltage level transmission iines individually.
According to an aspect of the present invention, it provides a method for de-icing all transmission Iines in a bipolar series MTDC system, wherein the method comprises: bypassing each converter of a kind of pole in all terminals and making ail transmission Iines of the kind of pole functioned under metaliic return mode; and reconnecting the converter in parallel with a converter of a contrary pole in the same terminal individually.
According to the other aspect of the present invention, it provides a method for de-icing low voltage level transmission Iines in a bipolar series MTDC system, wherein the method comprises: bypassing each converter of a kind of pole in all terminals and making all transmission Iines of the kind of pole functioned under metallic return mode; reconnecting the converter in low voltage level terminals in parallel with a converter of a contrary pole in the same terminals individually; and reconnecting the converter in high voltage level terminals in anti-parallel with the low voltage level terminals.
According to a preferred embodiment of the present invention, the converter (R1-) of a kind of pole in a low voitage level rectifier terminal is operated as rectifier to increase current through the low voltage level transmission lines between the low voltage level rectifier terminal (R1 ) and the high voltage level rectifier terminal (R2).
According to a preferred embodiment of the present invention, the converter (R2-) of a kind of pole in a high voltage level rectifier terminal is operated as inverter to decrease current through the high voitage level transmission lines between the high voltage level rectifier terminal (R2) and the high voltage level inverter terminal (12).
According to a preferred embodiment of the present invention, the converter (12-) of a kind of pole in a high voltage level inverter terminal is operated as rectifier to increase current through the low voltage level transmission lines between a low voitage level inverter terminal (11 ) and the high voltage level inverter terminai (I2).
According to a preferred embodiment of the present invention, the converter (11-) of a kind of pole in a low voltage level inverter terminal is operated as inverter.
According to another aspect of the present invention, it provides a method for de-icing low voltage level transmission lines in a 4-termial bipolar series MTDC system. The method comprises: on-line splitting the 4-terminai bipolar series MTDC system into two bipolar 2-termina! HVDC systems; bypassing each converter of a kind of pole in all terminals and making low voltage level transmission lines of the kind of pole functioned under metallic return mode; reconnecting the converter in parallel with a converter of a contrary pole in the same terminals individually.
According to a preferred embodiment of the present invention, the on-line splitting step further comprises: operating the high voltage level rectifier terminal (R2) as inverter terminal and the high voitage level inverter terminal (12) as rectifier terminal; connecting metallic return conductors and local earth electrodes of the high voltage level rectifier terminal (R2) and the high voltage level inverter terminal (12) between high voltage transmission line in positive pole and high voltage transmission line in the negative pole to form two return paths and bypassing the high voltage transmission lines; and disconnecting the high voltage transmission lines between the high voltage level rectifier terminal (R2) and the high voltage level inverter terminal (12).
According to a preferred embodiment of the present invention, the converters in a high voltage level rectifier terminal are operated as inverters and the converters in a high voltage level inverter terminal are operated as rectifiers.
According to a preferred embodiment of the present invention, the de-icing function on low voltage level transmission lines between the high voltage level terminals and low voltage level terminals is realized without impact on the current through high voltage level transmission lines between the high voltage level terminals.
According to another aspect of the present invention, it provides a method for de-icing a single group of low voltage level transmission lines in a 4-termial bipolar series MTDC system, wherein the method comprises: bypassing each converter of a kind of pole in all terminals, and making the transmission lines in the kind of pole functioned under metallic return mode; and reconnecting the converter in the low voltage level terminal in parallel with the converter of contrary pole in the same terminal individually; reconnecting the converter in the high voltage level terminal in anti-parallel with the low voltage level terminal.
According to a preferred embodiment of the present invention, the conversion mode of the converter of a kind of pole in a low voltage level terminal (R1-) is same to that of the converter of a contrary pole in the same terminal to increase current on the single group of the low voltage level transmission lines; and the conversion mode of the converter of a kind of pole in a high voltage level terminal (R2-) is contrary to that of the converter of a contrary pole in the same terminal to decrease current on the high voltage level transmission lines.
According to a preferred embodiment of the present invention, the method further comprises: reconnecting each converter of a kind of pole in two terminals which are connected via the other group of low voltage level transmission lines in the kind of pole in parallel with a converter of a contrary pole in the same terminal individualiy; and operating the converter of the kind of pole in the two terminals under a conversion mode which is the same as the conversion mode of the converters of a contrary pole in the same terminal individually.
According to a preferred embodiment of the present invention, the method further comprises: reconnecting each converter of a kind of pole in the high voltage level terminal and low voltage terminal which are connected via the other group of low voltage level transmission in the kind of pole in series with the series MTDC system; operating the converter of the kind of pole (12-) in the high voltage level terminal (12) under the conversion mode which is contrary to the conversion mode of the converter of a contrary pole in the same terminal; and operating the converter of the kind of pole in the low voltage level terminal (11 -) under the conversion mode which is the same as the conversion mode of the converter of a contrary pole in the same terminal.
According to a preferred embodiment of the present invention, the method further comprises: reconnecting each converter of a kind of pole in the high voltage level terminal and low voltage level terminal which are connected via the other group of low voltage level transmission line in said kind of pole in series with the series MTDC system; operating the converter of the kind of pole (12-) in the high voltage level terminal (12) under the conversion mode which is the same as the conversion mode of the converter the converter of a contrary pole in the same terminal; and operating the converter of the kind of pole (11-) in the low voltage level terminal (11 ) under the conversion mode which is contrary to the conversion mode of the converter of a contrary pole in the same terminal.
According to a preferred embodiment of the present invention, the de-icing function on a single group of low voltage level transmission lines in a 4-terminal bipolar series MTDC system is realized without impact on the current through other transmission lines in the 4-terminai bipolar series MTDC system.
According to a preferred embodiment of the present invention, the kind of pole can be negative pole or positive pole, and the contrary pole is positive pole or negative pole respectively.
According to another aspect of the present invention, it provides a method for de-icing high voltage level transmission lines in a 4-termial bipolar series MTDC system, wherein the method comprises: bypassing two high voltage level terminals of the system; and reconnecting the rectifier terminal of the two high voltage level terminals in parallel with the low voltage level rectifier terminal; and reconnecting the inverter terminal of the two high voltage level terminals in parallel with the low voltage level inverter terminal.
According to a preferred embodiment of the present invention, the de-icing function on high voltage level transmission lines between the high voltage level terminals is realized without impact on the current through low voltage level transmission lines between the high voltage level terminal and low voltage level terminal.
According to another aspect of the present invention, it provides a system utilizing any one of de-icing methods mentioned above.
Embodiments of the present invention propose methods for de-icing transmission lines in a 4-terminal bipolar series MTDC system and a system thereof, which facilitate the development of series MTDC applications and long distance transmission of power in low temperature area. With the proposed invention, the methods for de-icing of transmission lines won't cause MTDC system shutdown and temperature rise on undesired transmission lines.
BRIEF DESCRIPTION OF THE DRAWINGS
The subject matter of the invention will be explained in more details in the following description with reference to preferred exemplary embodiments which are illustrated in the drawings, in which:
Fig.1 illustrates a 4-terminal bipolar series MTDC system under normal operation according to prior art;
Fig.2a illustrates a configuration of 4-terminal bipolar series MTDC system for de-icing all transmission fines according to an embodiment of the present invention;
Fig.2b illustrates a configuration of 3-terminal bipolar series MTDC system for de-icing all transmission lines according to an embodiment of the present invention;
Fig.3a illustrates a configuration of 4-terminal bipolar series MTDC system for de-icing ail low voltage level transmission lines according to an embodiment of the present invention;
Figs.3b, 3c and 3d together illustrate a configuration of de-icing all low voltage level transmission lines for 4-terminal bipolar series MTDC system according to another embodiment of the present invention;
Fig.4 illustrates a configuration of 4-terminal bipolar series MTDC system for de-icing a single group of low voltage level transmission lines according to an embodiment of the present invention;
Fig.5a illustrates a configuration of 4-terminal bipolar series MTDC system for de-icing a single group of low voltage level transmission lines according to another embodiment of the present invention;
Fig.5b illustrates another configuration of 4-terminal bipolar series MTDC system for de-icing a single group of low voltage level transmission lines according to an embodiment of the present invention;
Fig.5c illustrates another configuration of 4-terminal bipolar series MTDC system for de-icing a single group of low voltage level transmission lines according to an embodiment of the present invention; and
Fig.6 illustrates a configuration of 4-terminal bipolar series MTDC system for de-icing high voltage level transmission lines according to an embodiment of the present invention;
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS Exemplary embodiments of the present invention are described in conjunction with the accompanying drawings hereinafter. For the sake of clarity and conciseness, not all the features of actual implementations are described in the specification.
Fig.2a illustrates a configuration of 4-terminal bipolar series MTDC system for de-icing all transmission lines according to an embodiment of the present invention.
As shown in Fig.2a, for de-icing all transmission lines in such 4-terminal bipolar series MTDC system, each converter of a kind of pole (for example the negative pole) in all terminals is bypassed by means of isolators or switches; all corresponding transmission lines are functioned under metallic return mode; and each of bypassed converters is re-connected in parallel with the converter of a contrary pole (for example the positive pole) in the same terminal individually. In detail, the converter R1- is connected to the converter R1+ in parallel, and so forth. When all the converters are operated with 4kA, the system current is high up to at least 8kA for melting the ice coating on transmission lines.
It should be noticed that, the operation current of converters should be coordinated to prevent over current on them.
it's obvious to the person skilled in art that the method for de-icing all transmission lines in such 4-terminal bipolar series MTDC system is not limited to operate all the converters in negative poles. Besides the solution shown in Fig.2a, ail converters in positive pole of each terminal can be bypassed and then reconnected to the corresponding converters in negative pole of the same terminals for de-icing all the transmission lines to achieve the same performance.
Fig.2b illustrates a 3-terminal bipolar series MTDC system. The 3-terminal bipolar series MTDC system comprises 3 terminals, such as the first low voltage- level terminal R1 , the first high voltage level terminal R2, and the second low voltage level terminal 11 ; each terminal comprises a converter in the positive pole and a converter in the negative pole. In this system, two terminals R1 and R2 are operated as rectifiers and the other terminal !1 is operated as inverter. The rated parameter of rectifier converter is 400kV/4kA and that of inverter converter is 800kV/4kA. The terminals R1 and R2 are respectively connected via low voltage level transmission lines, for example 400kV level; and R2 and 11 are connected via high voltage level transmission lines, for example 800kV level. In normal operation, all converters are connected in series, and the DC current through such converters is same each other, for example 4kA.
As shown in Fig.2b, for de-icing all transmission lines in a 3-terminal bipolar series MTDC system, each converter of a kind of pole (for example the negative pole) in all terminals is bypassed by means of isolators or switches; all corresponding transmission lines are functioned under metallic return mode; and each of bypassed converters is re-connected in parallel with the converter of a contrary pole (for example the positive pole) in the same terminal individually. In detail, the converter R1- is connected to the converter R1+ in parallel, and so forth. When all the converters are operated with 4kA, the system current is high up to at least 8kA for melting the ice coating on transmission lines.
It should be noticed that, the operation current of converters should be coordinated to prevent over current on them.
it's obvious to the person skilled in art that the method for de-icing all transmission lines in such 3-terminal bipolar series MTDC system is not limited to operate all the converters in negative poles. Besides the solution shown in Fig.2b, all converters in positive pole of each terminal can be bypassed and then reconnected to the corresponding converters in negative pole of the same terminals for de-icing all the transmission lines to achieve the same performance.
Fig.3a illustrates a configuration of 4-terminal bipolar series MTDC system for de-icing all low voltage level transmission lines according to an embodiment of the present invention.
As shown in Fig.3a, there are two transmission line groups with 400kV voltage level. One group is 400kV level lines between terminal R1 and terminal R2, the other is 400kV level lines between terminal 11 and terminal I2.
In detail, all converters in negative pole are bypassed firstly. And then the transmission lines in negative pole are operated under metallic return mode with grounding voltage level. With operation of additional isolators, such converters in low voltage level terminals are re-connected to the system in parallel with corresponding converter of the positive pole in the same terminal (R1- with R1 +, 11- with I1 +); and such converters in high voltage level terminals are re-connected to the system in anti-parallel with electrical adjacent low voltage level terminals (R2- with terminal R1 , 12- with terminal 11 ).
Thereafter, the converter R1- in the first low voltage level rectifier terminal is operated as rectifier to increase current through the low voltage level transmission lines between the first low voltage level rectifier terminal (R1 ) and the first high voltage level rectifier terminal (R2), i.e. to inject the additional current to +400kV level lines between R1 and R2.
The converter (R2-) in the first high voltage level rectifier terminal is operated as inverter to decrease current through the high voltage level transmission lines between the first high voltage level rectifier terminal (R2) and the second high voltage level inverter terminal (I2), i.e. to absorb additional current from +400kV level lines between R1 and R2 and inject the absorbed current to the related -400kV level lines, which now is operated under metallic return mode.
The converter (I2-) in the second high voltage level inverter terminal is operated as rectifier to increase current through the low voltage level transmission lines between a second low voltage level inverter terminal (11 ) and the second high voltage level inverter terminal (I2), i.e. to inject additional current absorbed from -400kV level lines (operated under metallic return mode) between 11 and I2 to the related +400kV level Sines.
The converter (11-) in the second low voltage level inverter terminal is operated as inverter, i.e. to absorb the additional current from +400kV level line between M and 12 and inject it to the related -400kV level line (operated under metallic return mode now).
Assuming all the converters are operated with rated current, the current through all the 400kV level lines can reach 8kA without influencing 800kV level lines. It should be noted that 50% of designed transmission capacity is lost because terminal R2 and 12 stop their bulk power conversion to the related AC grids and only provide the additional current for de-icing.
Figs.3b, 3c and 3d together illustrate a method for de-icing all low voltage level transmission lines of 4-terminal bipolar series MTDC system according to another embodiment of the present invention. In this method, the 4-terminal bipolar series MTDC system can be on-line split into two bipolar 2-terminal DC systems without system shutdown.
As shown in Fig.3b, conversion mode of high voltage level rectifier terminal R2 is changed to inverter and conversion mode of high voltage level inverter terminal 12 is changed to rectifier.
As shown in Fig.3c, after DC voltage of ±800kV level transmission lines is low and steady (for example a few kV), metallic return conductors and local earth electrodes of the high voltage level rectifier terminal (R2) and the high voltage level inverter terminal (12) are connected between +800kV transmission line and -800kV transmission line to form two return paths and bypass the ±800kV level transmission lines; and disconnecting the +800kV and -800kV high voltage transmission lines between the high voltage level rectifier terminal (R2) and the high voltage level inverter terminal (12). As shown in Fig.3d, after the on-line splitting of the 4-terminal bipolar series TDC system, the de-icing method, which is mentioned previously in the description for Fig.2a, is applied to each split 2-terminal DC system. Converters R1-, R2-, 11- and !2- are bypassed and all -400kV level transmission lines are operated under metallic return line mode. Then such converters are re-connected in parallel with the converters of the same terminal (R1- with R1 +, R2- with R2+, 11- with I1+, 12- with I2+).
Assuming all the converters are operated with rated current, the current through all the +400kV level lines can reach 8kA. It should be noted that the limitation of the method lies in that terminal R2 is normally located at power generation base, which means local load may be not sufficient to consume all the required power. Similar to R2, terminal 12 is normally designed to be at load center, which means there may be no enough power for de-icing.
Fig.4 illustrates a configuration of 4-terminal bipolar series MTDC system for de-icing a single group of low voltage level transmission lines according to an embodiment of the present invention.
As shown in Fig.4, only ±400kV level lines between terminal R1 and R2 need to be de-iced. Firstly, all converters of the MTDC system in the negative pole (R1-, R2-, 11- and I2-) are bypassed. And the transmission lines in negative pole are operated under metallic return mode with grounding voltage level. With the operation of additional isolators, the converter of the low voltage level terminal in negative pole is re-connected to the system in parallel with the converter of the positive pole in the same terminal (R1- with R1+); and the converter of the high voltage level terminal in negative pole is reconnected in anti-parallel with the low voltage level terminal (R2- with terminal R1).
For the status of converters in terminal R1 and R2, the conversion mode of the converter of the negative pole in a low voltage level terminal (R1-) is operated the same as that of the converter of the positive pole to increase current on the low voltage level transmission lines between the low voltage level terminal (R1 ) and the high voltage level terminal (R2); i.e. to inject the additional current to +400kV level lines between R1 and R2.
The conversion mode of the converter of the negative pole in the high voltage level terminal (R2-) is operated contrary to that of the converter of the positive pole to decrease current on the high voltage level transmission lines between high voltage level terminals; i.e. to absorb additional current from +400kV level lines between R1 and R2, and inject the absorbed current to the related -400kV level line (operated under metallic return mode now).
Fig.5a illustrates a configuration of 4-terminal bipolar series MTDC system for de-icing a single group of low voltage level transmission lines according to an embodiment of the present invention.
Besides the operation on the converters (R1 , R2) described above based on Fig.4, in Fig.5a, the method for de-icing a single group of low voltage level transmission lines between terminal R1 and R2 further comprises: besides bypassing each converter {12-, 11-) in two terminals (I2, 11 ) which are connected via the other group of low voltage level transmission lines, the converters (I2-, 11-) of the two terminals are reconnected in parallel with converters (I2+, 11 +) in the same terminal individually.
Assuming all converters are in operation, the reliability of the 4-terminal bipolar series MTDC system can be enhanced due to the alternative performance; for instance, converters (I1 +, 11-) and (I2+, I2-) can be the backup each other. However, the converted power of each terminal is reduced 50%.
Fig.5b illustrates another configuration of 4-terminal bipolar series MTDC system for de-icing a single group of low voltage level transmission lines according to an embodiment of the present invention.
As shown in Fig.5b, the converter 12- and converter 11- is reconnected to the MTDC system in series. The conversion mode of the converter (I2-) in the high voltage level terminal connected to the other group of low voltage level transmission lines is contrary to that of the converter of the positive pole (I2+) in the same terminal I2; and the conversion mode of a converter of negative pole in the low voltage level terminal (11-) connected to the other group of low voltage level transmission lines is the same as that of the converter (11 +) of the positive pole in the same terminal 11.
Assuming all converters are operated with rated current, the full power operation of terminal 11 can be ensured by the alternative embodiment. However, terminal 12 and R2 will stop the bulk power delivery to its AC grid.
Fig.5c illustrates another configuration of 4-terminal bipolar series MTDC system for de-icing a single group of low voltage level transmission lines according to an embodiment of the present invention. As shown in Fig.5c, the converter 12- and the converter i1- is reconnected to the MTDC system in series. The conversion mode of a converter (I2-) of the negative pole in the high voltage level terminal (I2) which is connected to the other group of low voltage level transmission lines is the same as that of the converter of the positive pole (I2+) in the same terminal (12); and the conversion mode of the converter (11-) of the negative pole in the low voltage level terminal (11 ) which is connected to the other group of low voltage level transmission lines is contrary to that of the converter of the positive pole (11+) in the same terminal.
Assuming all converters are operated with rated current, the fuil power operation of terminal 12 can be ensured by this alternative implementation. However, terminal 1 and R2 will stop the bulk power delivery to its AC grid.
According to above described embodiments, the de-icing function on a single group of low voltage level transmission lines in a 4-terminai bipolar series MTDC system is realized without impact on the current through other transmission lines in the 4-terminal bipolar series MTDC system.
Fig .6 illustrates a configuration of 4-terminal bipolar series MTDC system for de-icing high voltage level transmission lines according to an embodiment of the present invention.
As shown in Fig.6, the method for de-icing high voltage level transmission lines in a 4-termial bipolar series MTDC system comprises bypassing two high voltage level terminals of the system; and reconnecting the two high voltage level terminals in parallel with low voltage level terminals individually.
In detail, to realize de-icing of 800kV voltage level transmission lines in the exemplary 4-terminal bipolar series MTDC system, high voltage terminals (R2 and 12) are bypassed and then re-connected to the system in parallel (terminal R2 with terminal R1 , terminal !2 with terminal 11 ). Assuming all the converters are operated with rated current, it can be found the current flowing through 800kV level transmission lines can reach 8kA without influencing 400kV level lines.
The present invention also proposes a system, which utilizes above mentioned de-icing method.
Although the embodiments and accompanying drawings are taken to describe the spirit and concept of the innovation by operating the converters in negative pole, the person skilled in art appreciates that for de-icing the transmission lines in a series bipolar MTDC system, the converters in positive pole can be bypassed and reconnected to system correspondingly.
Compared with the existing prior arts, the proposed solution of the present invention is more practical and flexible for de-icing implementation on the series MTDC system. Referring to the description of the exemplary embodiments, those skilled in the art appreciate the advantages of the present invention:
1. The proposed de-icing methods will not cause MTDC system shutdown during de-icing of selected transmission lines.
2. No special operation on converter/transmission line is required for de-icing operation, and the traditional operation criterions can be satisfied during de-icing operation.
3. Based on the proposed methods, de-icing the target transmission lines will not cause undesired temperature rise on other lines.
4. Various configurations are proposed in the present invention, and greatly improve the flexibility of de-icing operation.
Though the present invention has been described on the basis of some preferred embodiments, those skilled in the art should appreciate that those embodiments should by no means limit the scope of the present invention. Without departing from the spirit and concept of the present invention, any variations and modifications to the embodiments should be within the apprehension of those with ordinary knowledge and skills in the art, and therefore fall in the scope of the present invention which is defined by the accompanied claims.

Claims

1. A method for de-icing all transmission lines in a bipolar series MTDC system, wherein said method comprises:
bypassing each converter of a kind of pole in ail terminals and making ail transmission lines of said kind of pole functioned under metallic return mode; and
reconnecting said converter in parallel with a converter of a contrary pole in the same terminal individually.
2. A method for de-icing low voltage level transmission lines in a 4-termial bipolar series MTDC system, wherein said method comprises:
bypassing each converter of a kind of pole in all terminals and making all transmission lines of said kind of pole functioned under metallic return mode; reconnecting said converter in low voltage level terminals in parallel with a converter of a contrary pole in the same terminals individually; and
reconnecting said converter in high voltage level terminals in anti-parallel with said low voltage level terminals.
3. The method according to claim 2, wherein said converter (R1-) of a kind of pole in a low voltage level rectifier terminal is operated as rectifier to increase current through said low voltage level transmission lines between said low voltage level rectifier terminal (R1) and the high voltage level rectifier terminal (R2).
4. The method according to claim 2, wherein said converter (R2-) of a kind of pole in a high voltage level rectifier terminal is operated as inverter to decrease current through the high voltage level transmission lines between said high voltage level rectifier terminal (R2) and the high voltage level inverter terminal (I2).
5. The method according to claim 2, wherein said converter (I2-) of a kind of pole in a high voltage level inverter terminal is operated as rectifier to increase current through the low voltage level transmission lines between a low voltage level inverter terminal (11 ) and said high voltage level inverter terminal (I2).
6. The method according to claim 2, wherein said converter (11-) of a kind of pole in a low voltage level inverter terminal is operated as inverter.
7. A method for de-icing low voltage level transmission lines in a 4-termial bipolar series MTDC system, wherein said method comprises:
on-line splitting said 4-terminal bipolar series MTDC system into two bipolar 2-temninal HVDC systems;
bypassing each converter of a kind of pole in all terminals and making low voltage level transmission lines of said kind of pole functioned under metallic return mode;
reconnecting said converter in parallel with a converter of a contrary pole in the same terminals individually.
8. The method according to claim 7, wherein said on-line splitting step further comprises:
operating said high voltage level rectifier terminal (R2) as inverter terminal and said high voltage level inverter terminal (12) as rectifier terminal; connecting metallic return conductors and local earth electrodes of said high voltage level rectifier terminal (R2) and said high voltage level inverter terminal (12) between high voltage transmission line in positive pole and high voltage transmission line in negative pole to form two return paths and bypassing high voltage transmission lines; and
disconnecting said high voltage transmission lines between said high voltage level rectifier terminal (R2) and said high voltage level inverter terminal (12).
9. The method according to claim 7, wherein said converters in a high voltage level rectifier terminal are operated as inverters and said converters in a high voltage level inverter terminal are operated as rectifiers.
10. The method according to claim 2 or 7, wherein the de-icing function on low voltage level transmission lines between said high voltage level terminals and low voltage level terminals is realized without impact on the current through high voltage level transmission lines between said high voltage level terminals.
11. A method for de-icing a single group of low voltage level transmission lines in a 4-termial bipolar series MTDC system, wherein said method comprises:
bypassing each converter of a kind of pole in ail terminals, and making the transmission lines in said kind of pole functioned under metallic return mode; and
reconnecting said converter in said low voltage level terminal in parallel with the converter of contrary pole in the same terminal individually;
reconnecting said converter in said high voltage level terminal in anti-parallel with said iow voltage level terminal.
12. The method according to claim 11 , wherein the conversion mode of said converter of a kind of pole in a low voltage level terminal (R1-) is same to that of said converter of a contrary pole in the same terminal to increase current on said single group of the low voltage level transmission lines; and
the conversion mode of said converter of a kind of pole in a high voltage level terminal (R2-) is contrary to that of said converter of a contrary pole in the same terminal to decrease current on the high voltage level transmission lines.
13. The method according to claim 11 , wherein said method further comprises
reconnecting each converter of a kind of pole in two terminals which are connected via the other group of low voltage level transmission lines in said kind of pole in parallel with a converter of a contrary pole in the same terminal individually; and
operating said converters of said kind of pole in said two terminals under a conversion mode which is the same as the conversion mode of said converter of a contrary pole in the same terminal individually.
14. The method according to claim 11 , wherein said method further comprises
reconnecting each converter of a kind of pole in the high voltage level terminal and low voltage level terminal which are connected via the other group of low voltage level transmission line in said kind of pole in series with the series TDC system;
operating said converter of said kind of pole (I2-) in said high voltage level terminal (12) under the conversion mode which is contrary to the conversion mode of the converter of a contrary pole in the same terminal; and operating said converter of said kind of pole (11-) in said low voltage level terminal (i1 ) under the conversion mode which is the same as the conversion mode of the converter of a contrary pole in the same terminal.
15. The method according to claim 11 , wherein said method further comprises
reconnecting each converter of a kind of pole in the high voltage level terminal and low voltage level terminal which are connected via the other group of low voltage level transmission line in said kind of pole in series with the series MTDC system;
operating said converter of said kind of pole (I2-) in said high voltage level terminal (I2) under the conversion mode which is the same as the conversion mode of the converter of a contrary pole in the same terminal; and operating said converter of said kind of pole (11-) in said low voltage level terminal (11 ) under the conversion mode which is contrary to the conversion mode of the converter of a contrary pole in the same terminal.
16. The method according to claim 11 , wherein the de-icing function on a single group of low voltage level transmission lines in a 4-terminal bipolar series MTDC system is realized without impact on the current through other transmission lines in said 4-terminal bipolar series MTDC system.
17. The method according to any one of above claims, wherein said kind of pole can be negative poie or positive pole, and said contrary pole is positive pole or negative poie respectively.
18. A method for de-icing high voltage level transmission lines in a 4-termial bipolar series MTDC system, wherein said method comprises:
bypassing two high voltage level terminals of said system; and
reconnecting the rectifier terminal of said two high voltage level terminals in parallel with the low voltage level rectifier terminal; and
reconnecting the inverter terminal of said two high voltage level terminals in parallel with the low voltage level inverter terminal.
19. The method according to claim 18, wherein the de-icing function on high voltage level transmission lines between said high voltage level terminals is realized without impact on the current through low voltage level transmission lines between said high voltage level terminal and low voltage level terminal.
20. A system, wherein said system utilizes a de-icing method according to any one of above claims.
PCT/CN2013/073794 2013-04-07 2013-04-07 Methods for de-icing transmission lines in bipolar series mtdc system and system thereof WO2014166026A1 (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN104655171A (en) * 2015-01-14 2015-05-27 西安工程大学 Electric transmission line simulation de-icing method based on concentrated load

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0937448A (en) * 1995-07-18 1997-02-07 Nissin Electric Co Ltd Snow-melting method of transmission line
CN102496898A (en) * 2011-11-16 2012-06-13 四川大学 Bifunctional direct current ice melting apparatus based on voltage source type current converter and ice melting method thereof
CN102642481A (en) * 2011-02-18 2012-08-22 株洲变流技术国家工程研究中心有限公司 Electricity energy regulating-ice melting device and method for railway traction network

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0937448A (en) * 1995-07-18 1997-02-07 Nissin Electric Co Ltd Snow-melting method of transmission line
CN102642481A (en) * 2011-02-18 2012-08-22 株洲变流技术国家工程研究中心有限公司 Electricity energy regulating-ice melting device and method for railway traction network
CN102496898A (en) * 2011-11-16 2012-06-13 四川大学 Bifunctional direct current ice melting apparatus based on voltage source type current converter and ice melting method thereof

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN104655171A (en) * 2015-01-14 2015-05-27 西安工程大学 Electric transmission line simulation de-icing method based on concentrated load

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