CN111969555B - Harmonic protection method and device for conventional direct current power transmission system - Google Patents

Harmonic protection method and device for conventional direct current power transmission system Download PDF

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CN111969555B
CN111969555B CN202010646827.5A CN202010646827A CN111969555B CN 111969555 B CN111969555 B CN 111969555B CN 202010646827 A CN202010646827 A CN 202010646827A CN 111969555 B CN111969555 B CN 111969555B
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direct current
harmonic
instruction
transmission system
voltage
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CN111969555A (en
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彭茂兰
冯雷
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Maintenance and Test Center of Extra High Voltage Power Transmission Co
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Maintenance and Test Center of Extra High Voltage Power Transmission Co
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
    • H02H3/50—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to the appearance of abnormal wave forms, e.g. ac in dc installations
    • H02H3/52—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to the appearance of abnormal wave forms, e.g. ac in dc installations responsive to the appearance of harmonics
    • 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
    • H02J1/00—Circuit arrangements for dc mains or dc distribution networks
    • H02J1/02—Arrangements for reducing harmonics or ripples

Abstract

The invention discloses a harmonic protection method and a harmonic protection device for a conventional direct current power transmission system, wherein the method is used for detecting the change rate of direct current line voltage and/or alternating current system voltage in real time; when the change rate/the change rate exceeds a first preset value or the voltage of the alternating current system is lower than a second preset value, sending a first control instruction to a timer, wherein the first control instruction comprises a starting instruction and a time setting instruction for the timer, and the starting instruction is used for starting timing operation; the time setting instruction is used for setting timing duration; acquiring the harmonic content of direct current voltage and the harmonic content of direct current; and within the timing duration, simultaneously meeting two criteria, and if the two criteria are met, sending a second control instruction to the direct current control protection system, wherein the second control instruction comprises the restart operation of the direct current control protection system instruction. According to the invention, after resonance occurs, resonance is eliminated through a certain control strategy, and normal operation of the direct-current power transmission system is ensured.

Description

Harmonic protection method and device for conventional direct current power transmission system
Technical Field
The invention relates to the technical field of conventional direct-current power transmission systems, in particular to a harmonic protection method of a conventional direct-current power transmission system.
Background
A conventional dc transmission system is a bipolar junction, as shown in fig. 1. Under certain specific operating parameter conditions, when a direct current transmission system is disturbed by lightning or alternating current system faults and the like, the direct current transmission system may generate resonance with a certain frequency, and overvoltage and overcurrent are generated on a high-voltage polar line.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides a harmonic protection method and a harmonic protection device for a conventional direct current transmission system, which are used for identifying direct current system resonance caused by lightning stroke or alternating current system fault, eliminating the resonance through a certain control strategy after the resonance occurs and ensuring the normal operation of the direct current transmission system.
In order to achieve the purpose, the technical scheme of the invention is as follows:
a harmonic protection method of a conventional direct current transmission system is used for a two-end direct current transmission system, the two-end direct current transmission system adopts a bipolar two-end neutral point grounding mode, and the method comprises the following steps:
real-time detection of DC line voltage UdLChange rate du/dt and ac system voltage Uac；
When the rate of change du/dt exceeds a first predetermined value, or the AC system voltage UacWhen the time is lower than a second preset value, sending a first control instruction to a timer, wherein the first control instruction comprises a starting instruction and a time setting instruction for the timer, and the starting instruction is used for starting timing operation; the time setting instruction is used for setting timing duration;
obtaining the harmonic content U of the DC voltagedharmHarmonic content of sum direct current Idharm；
Within the timing duration, the following criteria are simultaneously met, if the following criteria are met, a second control instruction is sent to the direct current control protection system, and the second control instruction comprises restarting operation of the direct current control protection system instruction;
criterion 1: judging the harmonic content U of the DC voltagedharmGreater than the third preset value and the harmonic content I of the direct currentdharmThe continuous time is greater than a fourth preset value and at least meets the first duration;
criterion 2: DC line voltage UdLAbsolute value of (1 | U)dL| is greater than a fifth preset value and the continuous time at least satisfies the second duration.
According to the conventional harmonic protection method for the direct current power transmission system, the timing duration is 1 s.
The conventional method for harmonic protection of a dc power transmission system as described above, further, the first duration is 500 ms.
The conventional method for harmonic protection of a dc power transmission system as described above, further, the second duration is 10 ms.
A harmonic protection system of a conventional direct current transmission system is used for a two-end direct current transmission system, the two-end direct current transmission system adopts a bipolar two-end neutral point grounding mode, and the harmonic protection system is characterized by comprising
A first detection unit for detecting the DC line voltage U in real timedLChange rate du/dt and ac system voltage Uac；
A timer for detecting when the rate of change du/dt exceeds a first preset value, or the AC system voltage UacWhen the time is lower than a second preset value, receiving a first control instruction from the first detection unit, wherein the first control instruction comprises a starting instruction for the timer and a time setting instruction, the starting instruction is used for starting timing operation, and the time setting instruction is used for setting timing duration;
a second detection unit for obtaining the harmonic content U of the DC voltagedharmHarmonic content of sum direct current Idharm；
The judging unit is used for judging whether the system meets the following criteria within the timing duration time, and if so, sending a second control instruction to the direct-current control protection system, wherein the second control instruction comprises the restarting operation of the direct-current control protection system instruction;
criterion 1: judging the harmonic content U of the DC voltagedharmGreater than the third preset value and the harmonic content I of the direct currentdharmThe continuous time is greater than a fourth preset value and at least meets the first duration;
criterion 2: DC line voltage UdLAbsolute value of (1 | U)dL| is greater than a fifth preset value and the continuous time at least satisfies the second duration.
The harmonic protection system of the conventional dc power transmission system as described above, further, the timing duration is 1 s.
The harmonic protection system of the conventional dc power transmission system as described above, further, the first duration is 500 ms.
The harmonic protection system of the conventional dc power transmission system as described above, further, the second duration is 10 ms.
Compared with the prior art, the invention has the beneficial effects that: the invention is applied to eliminating resonance by restarting a direct current system after resonance is caused by lightning stroke or alternating current system fault. The method comprises the steps of monitoring the voltage of a direct current line and the voltage of an alternating current system in real time to monitor whether lightning stroke or alternating current system fault occurs or not, monitoring the values of the harmonic content of the direct current voltage and the harmonic content of the direct current within set time after the lightning stroke or the alternating current system fault occurs, and eliminating resonance by restarting the direct current system if the values exceed the set criterion.
Drawings
FIG. 1 is a schematic diagram of a two terminal DC power transmission system using the method of the present invention;
fig. 2 is a schematic diagram of harmonic protection logic of a conventional dc power transmission system according to an embodiment of the present invention.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings and detailed description.
Example (b):
referring to fig. 1, the method is used for a two-terminal direct-current power transmission system, a bipolar system connection mode is a connection mode commonly adopted by direct-current power transmission engineering, the two-terminal direct-current power transmission system adopts a bipolar two-terminal neutral point grounding mode, and the bipolar two-terminal neutral point grounding mode can be regarded as two independent single-pole ground loop modes. The current directions of the positive pole and the negative pole in the ground loop are opposite, and the current in the ground is the difference value of the current of the two poles. In bipolar symmetrical operation, no current flows in the ground, or only a small amount of unbalanced current flows, typically less than 1% of the rated current. Therefore, when the bipolar symmetrical mode is operated, the problems of galvanic corrosion and the like caused by the current in the ground can be eliminated. When needed, the two poles can run asymmetrically, the currents in the two poles are not equal, and the current in the earth is the difference between the currents of the two poles. The length of the operation time is determined by the service life of the grounding electrode.
Referring to fig. 2, a conventional harmonic protection method for a two-terminal dc power transmission system, which uses a bipolar two-terminal neutral point grounding method, includes the following steps:
real-time detection of DC line voltage UdLChange rate du/dt and ac system voltage Uac；
When the rate of change du/dt exceeds a first predetermined value, or the AC system voltage UacWhen the time is lower than a second preset value, sending a first control instruction to a timer, wherein the first control instruction comprises a starting instruction and a time setting instruction for the timer, and the starting instruction is used for starting timing operation; the time setting instruction is used for setting timing duration, and the timing duration can be set according to the actual running condition of the direct current power transmission system, preferably 1 s;
obtaining the harmonic content U of the DC voltagedharmHarmonic content of sum direct current Idharm；
Within the timing duration, the following criteria are simultaneously met, if the following criteria are met, a second control instruction is sent to the direct current control protection system, and the second control instruction comprises restarting operation of the direct current control protection system instruction;
criterion 1: judging the harmonic content U of the DC voltagedharmGreater than the third preset value and the harmonic content I of the direct currentdharmThe continuous time is greater than the fourth preset value and at least meets a first duration, and the first duration can be set according to the actual operation condition of the direct current power transmission system, and is preferably 500 ms;
criterion 2: DC line voltage UdLAbsolute value of (1 | U)dLAnd | is greater than a fifth preset value, and the continuous time at least meets a second duration, wherein the second duration can be set according to the actual operation condition of the direct-current power transmission system, and is preferably 10 ms.
The working principle of the invention is as follows: the invention is applied to eliminating resonance by restarting a direct current system after resonance is caused by lightning stroke or alternating current system fault. The method comprises the steps of monitoring the voltage of a direct current line and the voltage of an alternating current system in real time to monitor whether lightning stroke or alternating current system fault occurs or not, monitoring the values of the harmonic content of the direct current voltage and the harmonic content of the direct current within set time after the lightning stroke or the alternating current system fault occurs, and eliminating resonance by restarting the direct current system if the values exceed the set criterion.
The above embodiments are only for illustrating the technical concept and features of the present invention, and the purpose thereof is to enable those skilled in the art to understand the contents of the present invention and implement the present invention accordingly, and not to limit the protection scope of the present invention accordingly. All equivalent changes or modifications made in accordance with the spirit of the present disclosure are intended to be covered by the scope of the present disclosure.

Claims (10)

1. A harmonic protection method of a conventional direct current transmission system is used for a two-end direct current transmission system, the two-end direct current transmission system adopts a bipolar two-end neutral point grounding mode, and the method is characterized by comprising the following steps:
real-time detection of DC line voltage UdLChange rate du/dt and ac system voltage Uac；
When the rate of change du/dt exceeds a first predetermined value, or the AC system voltage UacWhen the time is lower than a second preset value, sending a first control instruction to a timer, wherein the first control instruction comprises a starting instruction and a time setting instruction for the timer, and the starting instruction is used for starting timing operation; the time setting instruction is used for setting timing duration;
obtaining the harmonic content U of the DC voltagedharmHarmonic content of sum direct current Idharm；
Within the timing duration, the following criteria are simultaneously met, if the following criteria are met, a second control instruction is sent to the direct current control protection system, and the second control instruction comprises restarting operation of the direct current control protection system instruction;
criterion 1: judging the harmonic content U of the DC voltagedharmGreater than the third preset value and the harmonic content I of the direct currentdharmThe continuous time is greater than a fourth preset value and at least meets the first duration;
criterion 2: DC line voltage UdLAbsolute value of (1 | U)dL| is greater than a fifth preset value and the continuous time at least satisfies the second duration.
2. The conventional dc power transmission system harmonic protection method of claim 1 wherein the timed duration is 1 s.
3. The conventional direct current power transmission system harmonic protection method of claim 1, wherein the first duration is 500 ms.
4. The conventional direct current power transmission system harmonic protection method of claim 1, wherein the second duration is 10 ms.
5. The harmonic protection method of claim 1, wherein the harmonic content U of the dc voltage is obtained by a bandpass filterdharmHarmonic content of sum direct current Idharm。
6. A harmonic protection system of a conventional direct current transmission system is used for a two-end direct current transmission system, the two-end direct current transmission system adopts a bipolar two-end neutral point grounding mode, and the harmonic protection system is characterized by comprising
A first detection unit for detecting the DC line voltage U in real timedLChange rate du/dt and ac system voltage Uac；
A timer for detecting when the rate of change du/dt exceeds a first preset value, or the AC system voltage UacWhen the value is lower than the second preset value, receivingA first control instruction from the first detection unit, wherein the first control instruction includes a start instruction for the timer and a time setting instruction, the start instruction is used for starting a timing operation, and the time setting instruction is used for setting a timing duration;
a second detection unit for obtaining the harmonic content U of the DC voltagedharmHarmonic content of sum direct current Idharm；
The judging unit is used for judging whether the system meets the following criteria within the timing duration time, and if so, sending a second control instruction to the direct-current control protection system, wherein the second control instruction comprises the restarting operation of the direct-current control protection system instruction;
criterion 1: judging the harmonic content U of the DC voltagedharmGreater than the third preset value and the harmonic content I of the direct currentdharmThe continuous time is greater than a fourth preset value and at least meets the first duration;
criterion 2: DC line voltage UdLAbsolute value of (1 | U)dL| is greater than a fifth preset value and the continuous time at least satisfies the second duration.
7. The conventional direct current transmission system harmonic protection system of claim 6 wherein the timed duration is 1 s.
8. The conventional direct current power transmission system harmonic protection system of claim 6 wherein the first duration is 500 ms.
9. The conventional direct current transmission system harmonic protection system of claim 6 wherein the second duration is 10 ms.
10. The harmonic protection system of claim 6 wherein the second detection unit is a band pass filter.
CN202010646827.5A 2020-07-07 2020-07-07 Harmonic protection method and device for conventional direct current power transmission system Active CN111969555B (en)

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CN112803468B (en) * 2021-01-20 2023-03-10 中国南方电网有限责任公司 AC/DC complementary resonance suppression control method and device

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CN203688720U (en) * 2013-06-19 2014-07-02 国家电网公司 Fault detection system for DC transmission grounding electrode circuits
CN105277848A (en) * 2014-06-23 2016-01-27 南京南瑞继保电气有限公司 Fault position identification method during DC harmonic protection action
CN104052034A (en) * 2014-07-04 2014-09-17 南京南瑞继保电气有限公司 Method for preventing high-voltage and direct-current transmission 50 Hz harmonic protection maloperation
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