CN-121983926-A - Flexible direct-current transmission line protection method and device based on breaker action voltage

CN121983926ACN 121983926 ACN121983926 ACN 121983926ACN-121983926-A

Abstract

The application provides a flexible direct current transmission line protection method and device based on a breaker action voltage. And calculating the fault voltage of the flexible direct current transmission line and the action voltage of the circuit breaker according to the refractive index and the reflection coefficient at the outlet of the converter station. And determining a dead zone identification time window according to the corresponding length when the flexible direct current transmission line fails. And protecting the flexible direct current transmission line according to the fault voltage of the flexible direct current transmission line, the action voltage of the circuit breaker and the dead zone identification time window. The method and the device can effectively distinguish the end faults in the area from the near end faults outside the area, improve the protection reliability of the flexible direct current transmission line, and ensure the safe and stable operation of the flexible direct current transmission system.

Inventors

WU WENXIANG
BAI RUNQING
LIU MING
Cui Die
ZHANG YONGXIN
SONG LINWEI
MA GUOQIANG
LIU PANPAN

Assignees

中国电力科学研究院有限公司
国网甘肃省电力公司超高压公司
国家电网有限公司直流技术中心
国家电网有限公司

Dates

Publication Date: 20260505
Application Date: 20251223

Claims (14)

1. The flexible direct current transmission line protection method based on the breaker action voltage is characterized by comprising the following steps of: Calculating fault voltage of the flexible direct current transmission line and action voltage of the circuit breaker according to the refractive index and the reflection coefficient at the outlet of the converter station; Determining a dead zone identification time window according to the corresponding length when the flexible direct current transmission line fails; And protecting the flexible direct current transmission line according to the fault voltage of the flexible direct current transmission line, the action voltage of the circuit breaker and the dead zone identification time window.
2. The method of claim 1, wherein, Under the condition that the tail end in the occurrence area of the flexible direct current transmission line is in fault, the fault voltage of the flexible direct current transmission line meets the following conditions: Under the condition that the flexible direct current transmission line generates a near-end fault outside the area, the fault voltage of the flexible direct current transmission line meets the following conditions: Wherein, the Representing a first fault voltage of the flexible direct current transmission line, Representing a second fault voltage of the flexible direct current transmission line, A third fault voltage representing the flexible direct current transmission line; representing the reflection coefficient at the outlet of the converter station M, Representing the reflection coefficient at the outlet of the converter station N, Representing the reflection coefficient at the fault point; Representing the refractive index at the outlet of the converter station N, Representing the refractive index at the point of failure; Representing an initial voltage when the flexible direct current transmission line fails; Representing the transfer function of the flexible direct current transmission line, meeting the following conditions ; Representing the attenuation coefficient of the line mode traveling wave, Representing the dispersion coefficient of the line mode traveling wave, Representing the propagation distance of the linear mode travelling wave, Representing the propagation velocity of the linear mode travelling wave, Representing the laplace operator.
3. The method of claim 1, wherein, Under the condition that the tail end in the flexible direct current transmission line generation area is in fault, the action voltage of the circuit breaker meets the following conditions: Under the condition that the flexible direct current transmission line generates a near-end fault outside the area, the action voltage of the circuit breaker meets the following conditions: Wherein, the Representing a first action voltage of a circuit breaker positioned at the head end of the flexible direct current transmission line, Representing a second action voltage of a breaker positioned at the head end of the flexible direct current transmission line, Representing an initial action voltage of a circuit breaker positioned at the tail end of the flexible direct current transmission line; representing the reflection coefficient at the outlet of the converter station M, Representing the reflection coefficient at the outlet of the converter station N, Representing the reflection coefficient at the fault point; Representing the refractive index at the outlet of the converter station N, Representing the refractive index at the point of failure, Representing the transfer function of the flexible direct current transmission line, meeting the following conditions ; Representing the attenuation coefficient of the line mode traveling wave, Representing the dispersion coefficient of the line mode traveling wave, Representing the propagation distance of the linear mode travelling wave, Representing the propagation velocity of the linear mode travelling wave, Representing the laplace operator.
4. The protection method according to claim 1, characterized in that the dead zone identification time window satisfies: Wherein, the Representing the deadband identification time window; indicating the end-of-zone fault impact factor, Representing the head-end fault influence factor outside the zone; Representing the corresponding length of the flexible direct current transmission line when the tail end in the generating area fails, Representing the corresponding length of the flexible direct current transmission line when the near end outside the generating area fails; Representing the propagation velocity of the linear mode travelling wave; indicating the time of action of the circuit breaker, Indicating the protection delay time, satisfying 。
5. The protection method according to claim 1, wherein the protecting the flexible direct current transmission line according to the fault voltage of the flexible direct current transmission line, the action voltage of the circuit breaker, and the dead zone identification time window includes: Performing wavelet transformation on fault voltage of the flexible direct current transmission line and action voltage of the circuit breaker in the dead zone identification time window to obtain a wavelet transformation mode maximum value; identifying the fault type of the flexible direct current transmission line according to the wavelet transformation module maximum value; and triggering a circuit breaker to protect the flexible direct current transmission line according to the fault type.
6. The protection method according to claim 5, wherein the identifying the fault type of the flexible dc transmission line according to the wavelet transformation module maximum value includes: Counting the number of effective voltages, wherein the effective voltages are used for indicating the maximum value of a wavelet transformation module which is larger than a preset voltage threshold; and if the number of the effective voltages is 2, judging that the near-end fault outside the flexible direct current transmission line occurs.
7. A flexible direct current transmission line circuit breaker based on breaker action voltage, comprising: the calculation module is used for calculating the fault voltage of the flexible direct current transmission line and the action voltage of the circuit breaker according to the refractive index and the reflection coefficient at the outlet of the converter station; The determining module is used for determining a dead zone identification time window according to the corresponding length when the flexible direct current transmission line fails; And the protection module is used for protecting the flexible direct current transmission line according to the fault voltage of the flexible direct current transmission line, the action voltage of the circuit breaker and the dead zone identification time window.
8. The circuit breaker according to claim 7, wherein, Under the condition that the tail end in the flexible direct current transmission line generation area fails, the calculation module calculates the failure voltage of the flexible direct current transmission line according to the following formula: under the condition that the flexible direct current transmission line generates a near-end fault outside the area, the calculation module calculates the fault voltage of the flexible direct current transmission line according to the following formula: Wherein, the Representing a first fault voltage of the flexible direct current transmission line, Representing a second fault voltage of the flexible direct current transmission line, A third fault voltage representing the flexible direct current transmission line; representing the reflection coefficient at the outlet of the converter station M, Representing the reflection coefficient at the outlet of the converter station N, Representing the reflection coefficient at the fault point; Representing the refractive index at the outlet of the converter station N, Representing the refractive index at the point of failure; Representing an initial voltage when the flexible direct current transmission line fails; Representing the transfer function of the flexible direct current transmission line, meeting the following conditions ; Representing the attenuation coefficient of the line mode traveling wave, Representing the dispersion coefficient of the line mode traveling wave, Representing the propagation distance of the linear mode travelling wave, Representing the propagation velocity of the linear mode travelling wave, Representing the laplace operator.
9. The circuit breaker according to claim 7, wherein, Under the condition that the tail end in the flexible direct current transmission line generation area fails, the calculation module calculates the action voltage of the circuit breaker according to the following formula: under the condition that the flexible direct current transmission line generates a near-end fault outside the area, the calculation module calculates the action voltage of the circuit breaker according to the following formula: Wherein, the Representing a first action voltage of a circuit breaker positioned at the head end of the flexible direct current transmission line, Representing a second action voltage of a breaker positioned at the head end of the flexible direct current transmission line, Representing an initial action voltage of a circuit breaker positioned at the tail end of the flexible direct current transmission line; representing the reflection coefficient at the outlet of the converter station M, Representing the reflection coefficient at the outlet of the converter station N, Representing the reflection coefficient at the fault point; Representing the refractive index at the outlet of the converter station N, Representing the refractive index at the point of failure, Representing the transfer function of the flexible direct current transmission line, meeting the following conditions ; Representing the attenuation coefficient of the line mode traveling wave, Representing the dispersion coefficient of the line mode traveling wave, Representing the propagation distance of the linear mode travelling wave, Representing the propagation velocity of the linear mode travelling wave, Representing the laplace operator.
10. The circuit breaker of claim 7, wherein the determination module calculates the dead zone identification time window as follows: Wherein, the Representing the deadband identification time window; indicating the end-of-zone fault impact factor, Representing the head-end fault influence factor outside the zone; Representing the corresponding length of the flexible direct current transmission line when the tail end in the generating area fails, Representing the corresponding length of the flexible direct current transmission line when the near end outside the generating area fails; Representing the propagation velocity of the linear mode travelling wave; indicating the time of action of the circuit breaker, Indicating the protection delay time, satisfying 。
11. The circuit breaker according to claim 7, characterized in that said protection module is specifically adapted to: Performing wavelet transformation on fault voltage of the flexible direct current transmission line and action voltage of the circuit breaker in the dead zone identification time window to obtain a wavelet transformation mode maximum value; identifying the fault type of the flexible direct current transmission line according to the wavelet transformation module maximum value; and triggering a circuit breaker to protect the flexible direct current transmission line according to the fault type.
12. The circuit breaker according to claim 11, characterized in that said protection module is specifically adapted to: Counting the number of effective voltages, wherein the effective voltages are used for indicating the maximum value of a wavelet transformation module which is larger than a preset voltage threshold; and if the number of the effective voltages is 2, judging that the near-end fault outside the flexible direct current transmission line occurs.
13. A computer device, comprising: one or more processors; The processor is used for storing one or more programs; The protection method of any one of claims 1 to 6 is implemented when the one or more programs are executed by the one or more processors.
14. A computer-readable storage medium, on which a computer program is stored, which computer program, when executed, implements the protection method according to any one of claims 1 to 6.

Description

Flexible direct-current transmission line protection method and device based on breaker action voltage Technical Field The application relates to the technical field of direct-current transmission, in particular to a flexible direct-current transmission line protection method and device based on breaker action voltage. Background The flexible direct current power transmission can realize smooth access, reliable delivery, flexible consumption, optimal configuration and the like of large-scale renewable energy sources, and is an important technical means for supporting and constructing an electric power system taking new energy sources as main bodies. However, the low damping characteristic of the flexible direct current transmission system easily causes fast rise rate of fault current and large influence range, and easily causes locking of the converter and irreversible damage of power electronic devices. In order to realize the rapid fault isolation and safe and stable operation of the flexible direct current transmission system, the flexible direct current transmission line needs to be protected. The related art is mostly based on boundary characteristics of a flexible direct current transmission system, and protection of the flexible direct current transmission line is achieved by combining fault voltage. However, for the flexible direct current transmission system without boundary, no obvious boundary exists between the flexible direct current transmission lines, and the transient characteristics of the flexible direct current transmission lines under the condition that the flexible direct current transmission lines where the circuit breakers are located are similar to those under the condition that the flexible direct current transmission lines are in terminal faults (namely terminal faults in areas) and near-end faults outside areas, so that dead zones exist in protection, and reliability is insufficient. Disclosure of Invention In order to solve the problem of insufficient reliability in the prior art, the application provides a flexible direct current transmission line protection method and device based on a breaker action voltage. In a first aspect, the present application provides a flexible dc transmission line protection method based on a breaker action voltage, which may include: And calculating the fault voltage of the flexible direct current transmission line and the action voltage of the circuit breaker according to the refractive index and the reflection coefficient at the outlet of the converter station. And determining a dead zone identification time window according to the corresponding length when the flexible direct current transmission line fails. And protecting the flexible direct current transmission line according to the fault voltage of the flexible direct current transmission line, the action voltage of the circuit breaker and the dead zone identification time window. In some possible implementations, in the case of an end fault in the flexible direct current transmission line occurrence area, the fault voltage of the flexible direct current transmission line satisfies: Under the condition that the flexible direct current transmission line generates a near-end fault outside the area, the fault voltage of the flexible direct current transmission line meets the following conditions: Wherein, the Representing a first fault voltage of the flexible direct current transmission line,Representing a second fault voltage of the flexible direct current transmission line,Representing a third fault voltage of the flexible direct current transmission line.Representing the reflection coefficient at the outlet of the converter station M,Representing the reflection coefficient at the outlet of the converter station N,Representing the reflection coefficient at the point of failure.Representing the refractive index at the outlet of the converter station N,Representing the refractive index at the point of failure.And the initial voltage when the flexible direct current transmission line fails is represented. Representing the transfer function of the flexible direct current transmission line, meeting。Representing the attenuation coefficient of the line mode traveling wave,Representing the dispersion coefficient of the line mode traveling wave,The propagation distance of the linear mode traveling wave is represented,Representing the propagation velocity of the linear mode traveling wave,Representing the laplace operator. In other possible implementations, in the case of an end fault in the flexible direct current transmission line occurrence zone, the action voltage of the circuit breaker satisfies: Under the condition that the flexible direct current transmission line generates a near-end fault outside the zone, the action voltage of the circuit breaker meets the following conditions Wherein, the Representing a first operating voltage of a circuit breaker located at the head end of the flexible direc