CN110265980B - UPFC (unified power flow controller) and fixed series compensation C-containing hybrid compensation line protection method based on correlation analysis - Google Patents

UPFC (unified power flow controller) and fixed series compensation C-containing hybrid compensation line protection method based on correlation analysis Download PDF

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CN110265980B
CN110265980B CN201910434369.6A CN201910434369A CN110265980B CN 110265980 B CN110265980 B CN 110265980B CN 201910434369 A CN201910434369 A CN 201910434369A CN 110265980 B CN110265980 B CN 110265980B
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CN110265980A (en
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束洪春
段丹妮
刘旭晗
蒋晓涵
田鑫萃
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Kunming University of Science and Technology
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/08—Locating faults in cables, transmission lines, or networks
    • G01R31/081—Locating faults in cables, transmission lines, or networks according to type of conductors
    • G01R31/086—Locating faults in cables, transmission lines, or networks according to type of conductors in power transmission or distribution networks, i.e. with interconnected conductors
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
    • H02H7/26—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/18—Arrangements for adjusting, eliminating or compensating reactive power in networks
    • H02J3/1807—Arrangements for adjusting, eliminating or compensating reactive power in networks using series compensators
    • H02J3/1814—Arrangements for adjusting, eliminating or compensating reactive power in networks using series compensators wherein al least one reactive element is actively controlled by a bridge converter, e.g. unified power flow controllers [UPFC]
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
    • Y02E40/10—Flexible AC transmission systems [FACTS]

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Emergency Protection Circuit Devices (AREA)
  • Supply And Distribution Of Alternating Current (AREA)

Abstract

The invention relates to a UPFC and fixed series compensation C-containing hybrid compensation line protection method based on correlation analysis, and belongs to the technical field of power system relay protection. When the mixed compensation line has single-phase earth fault, firstly, the direction elements R at two ends of the line are passed1、R2Respectively obtaining two groups of transient quantities of fault voltage and current, respectively intercepting the voltage and current transient quantities 3ms after the fault, carrying out 8-scale wavelet decomposition on the voltage and current transient quantities, then selecting a wavelet coefficient under a first scale to carry out correlation analysis, and finally constructing an inside-area fault criterion and an outside-area fault criterion according to the wavelet coefficient correlation under the first scale to realize the identification of the inside-area fault and the outside-area fault of the mixed compensation circuit containing the UPFC and the fixed series compensation C.

Description

UPFC (unified power flow controller) and fixed series compensation C-containing hybrid compensation line protection method based on correlation analysis
Technical Field
The invention relates to a UPFC and fixed series compensation C-containing hybrid compensation line protection method based on correlation analysis, and belongs to the technical field of power system relay protection.
Background
When a power system fails, a failure component ranging from a power frequency to a high frequency is generated, and the high frequency component contains a large amount of information such as the type, position, direction, degree, duration, and the like of the failure. Effective extraction and application of the information become important means for improving relay protection performance, and the protection speed can be improved to the maximum extent by using the transient quantity of the line fault to form a line protection criterion. In recent years, with the development of signal processing tools such as wavelet analysis, a series of new principles of ultra-high-speed protection using fault transients have been developed.
In order to meet the increasing power load demand and improve the transmission capacity of the existing transmission line as much as possible on the premise of avoiding the construction of a transmission channel, a Unified Power Flow Controller (UPFC) with the strongest function and the best characteristics is taken as a representative, and a flexible alternating current transmission device (FACTS) is widely applied to a power system. Although the strong control capability of the UPFC brings great benefits to the operation of a power system, the access of the UPFC also makes the transient process of the power grid fault become more and more complex, and brings many new problems to the relay protection, and the UPFC is embodied in the following aspects:
(1) the relay protection is influenced by different installation places and compensation modes of the UPFC;
(2) the transient component generated by the UPFC influences relay protection;
(3) when the UPFC is adjusted rapidly, the influence of rapid change of system parameters on relay protection is caused.
The fixed series compensation capacitor (C) + UPFC controllable phase shift technology can achieve the same effect as pure UPFC, and the UPFC and fixed series compensation mixed scheme can greatly reduce the construction cost on the premise of achieving the equivalent power flow control effect.
Disclosure of Invention
The invention aims to solve the technical problem of providing a UPFC and fixed series compensation C mixed compensation line protection method based on correlation analysis, and aims to solve the problem.
The technical scheme of the invention is as follows: a mixed compensation line protection method based on correlation analysis and including UPFC and fixed series compensation C is characterized in that when a mixed compensation line has a single-phase earth fault, the mixed compensation line firstly passes through a direction element R at the end M, N1、R2Obtaining transient quantities of two sets of fault voltages and currents, respectively, i.e.
Figure BDA0002070054280000011
And
Figure BDA0002070054280000012
and
Figure BDA0002070054280000013
secondly, respectively intercepting the voltage and current transient state quantity 3ms after the fault and carrying out 8-scale wavelet decomposition on the voltage and current transient state quantity, then selecting the wavelet coefficient under the first scale to carry out correlation analysis, and solving two groups of correlation coefficients
Figure BDA0002070054280000014
The positive direction of the specified current is the direction of the bus pointing to the line, and the inside and the outside of the correlation construction area of the wavelet coefficient under the 1 st scale of the voltage and the current detected at the head end and the tail end are usedThe fault criterion is that
Figure BDA0002070054280000015
And is
Figure BDA0002070054280000016
The MN section in the area is in failure; if it is
Figure BDA0002070054280000017
And is
Figure BDA0002070054280000018
The PM section fault outside the system area is detected; if it is
Figure BDA0002070054280000021
And is
Figure BDA0002070054280000022
Then it is a system out-of-zone NQ segment failure.
The method comprises the following specific steps:
step 1: when the hybrid compensation line has single-phase earth fault, firstly passes through the direction element R at the end M, N1、R2Obtaining transient quantities of two sets of fault voltages and currents, respectively, i.e.
Figure BDA0002070054280000023
And
Figure BDA0002070054280000024
and
Figure BDA0002070054280000025
step 2: respectively intercepting voltage and current transient components 3ms after the fault and performing 8-scale wavelet decomposition on the voltage and current transient components, wherein the wavelet basis function is selected as db 8;
step 3: wavelet coefficients under the first scale of voltage and current transient are respectively selected for correlation analysis, and two groups of correlation coefficients r are obtainedu,iComprises the following steps:
Figure BDA0002070054280000026
where k is the number of current transformers in the line connected to the bus in the event of a fault, N is the total number of current transformers in the line connected to the bus, d1_u(k)、d1_i(k) Wavelet coefficients under a first scale of voltage transient and current transient are respectively;
step 4: judging a fault;
if it is
Figure BDA0002070054280000027
And is
Figure BDA0002070054280000028
The MN section in the area is in failure;
if it is
Figure BDA0002070054280000029
And is
Figure BDA00020700542800000210
The PM section fault outside the system area is detected;
if it is
Figure BDA00020700542800000211
And is
Figure BDA00020700542800000212
The system area is an NQ section fault;
wherein the content of the first and second substances,
Figure BDA00020700542800000213
respectively representing the voltage-current correlation coefficient of the M side and the N side.
The wavelet coefficient under the first scale of the voltage and the current detected by the equivalent measuring end is inversely correlated, and the threshold value r of the correlation coefficientset1-0.4; the wavelet coefficient under the first scale of the voltage and the current detected by the equivalent measuring end is positively correlated, and the threshold value r of the correlation coefficientset2＝0.4。
The invention has the beneficial effects that:
(1) the fault voltage transient quantity and the fault current transient quantity are jointly used for protection, and the risk that the reliability of protection is reduced due to the use of a single type of transient quantity is effectively reduced.
(2) The wavelet transform and the correlation analysis are used, the interference of noise signals is effectively reduced by the wavelet transform, and the waveform similarity is directly quantized by the correlation analysis, so that the protection accuracy is improved to the maximum extent.
(3) By adopting a UPFC + C hybrid compensation mode, the identification of the internal and external faults of the area can be reliably realized no matter where the fault point is located on the line, and a good power flow control effect is realized.
(4) And by utilizing a mixed scheme of UPFC and fixed series compensation C, the construction cost is greatly reduced.
Drawings
FIG. 1 is a simulation model diagram of a hybrid compensation circuit including UPFC and fixed series C according to the present invention;
FIG. 2 is a waveform diagram of line transmission power under different compensation conditions in embodiment 1 of the present invention;
fig. 3 is a waveform diagram of the capacity ratio of UPFC + C in the hybrid compensation mode in embodiment 1 of the present invention;
fig. 4 is a waveform diagram of a wavelet coefficient of a first scale of M-side voltage and current high frequency in a short time window when a fault location is F1 in embodiment 2 of the present invention;
fig. 5 is a waveform diagram of a wavelet coefficient of a first scale of high frequency of voltage and current on the N side in a short time window when the fault location is F1 in embodiment 2 of the present invention;
fig. 6 is a waveform diagram of a wavelet coefficient of a first scale of M-side voltage and current high frequency in a short time window when a fault location is F2 in embodiment 3 of the present invention;
fig. 7 is a waveform diagram of a wavelet coefficient of a first scale of high frequency of voltage and current on the N side in a short time window when the fault location is F2 in embodiment 3 of the present invention;
fig. 8 is a waveform diagram of a wavelet coefficient of a first scale of M-side voltage and current high frequency in a short time window when a fault location is F4 in embodiment 4 of the present invention;
fig. 9 is a waveform diagram of the wavelet coefficient of the first scale of the high frequency of the voltage and the current on the N side in the short time window when the fault position is F4 in embodiment 4 of the present invention.
Detailed Description
The invention is further described with reference to the following drawings and detailed description.
Example 1: a 220kV mixed compensation circuit simulation model containing UPFC and fixed series compensation C is shown in FIG. 1; the circuit parameters are as follows: the line length of the PM branch is 100km, the line lengths of the ME branch and the FN branch are both 75km, and the line length of the NQ branch is 120 km. Fault location: the ME tributary fails 30km from the M terminal. The sampling frequency is 1 MHz. The fixed series compensation C is 20.5 muF. The failure initial time t is 0.17 s.
As can be seen from fig. 2, the line transmission power flow is optimized under the conditions of UPFC compensation and UPFC + C hybrid compensation. Compared with a UPFC compensation mode, the UPFC + C hybrid compensation mode greatly reduces the construction cost on the premise of achieving a considerable power flow control effect. As can be seen from fig. 3, in the hybrid compensation mode, the ratio of the UPFC capacity to the fixed series compensation C capacity is approximately 1: and 5, a better power flow control effect can be achieved.
Example 2: a 220kV mixed compensation circuit simulation model containing UPFC and fixed series compensation C is shown in FIG. 1; the circuit parameters are as follows: the line length of the PM branch is 100km, the line lengths of the ME branch and the FN branch are both 75km, and the line length of the NQ branch is 120 km. Fault location: the PM branch has a fault 10km away from the M end. The sampling frequency is 1 MHz. The fixed series compensation C is 20.5 muF. The failure initial time t is 0.17 s.
(1) According to the direction element R at end M, N after the first step of fault occurs in the specification1、R2Obtaining transient quantities of two sets of fault voltages and currents, respectively, i.e.
Figure BDA0002070054280000041
And
Figure BDA0002070054280000042
and
Figure BDA0002070054280000043
(2) and respectively intercepting the voltage transient and the current transient 3ms after the fault according to a second step in the specification and carrying out 8-scale wavelet decomposition on the voltage transient and the current transient.
(3) According to the descriptionSelecting wavelet coefficients under the first scale of voltage and current transient states as shown in figures 4 and 5 for correlation analysis, and obtaining two groups of correlation coefficients
Figure BDA0002070054280000044
(4) Correlation coefficient
Figure BDA0002070054280000045
Satisfy the requirement of
Figure BDA0002070054280000046
Correlation coefficient
Figure BDA0002070054280000047
Satisfy the requirement of
Figure BDA0002070054280000048
An out-of-zone PM leg fault may be determined.
Example 3: a 220kV mixed compensation circuit simulation model containing UPFC and fixed series compensation C is shown in FIG. 1; the circuit parameters are as follows: the line length of the PM branch is 100km, the line lengths of the ME branch and the FN branch are both 75km, and the line length of the NQ branch is 120 km. Fault location: the ME leg failed 25km from the M terminal. The sampling frequency is 1 MHz. The fixed series compensation C is 20.5 muF. The failure initial time t is 0.17 s.
(1) According to the direction element R at end M, N after the first step of fault occurs in the specification1、R2Obtaining transient quantities of two sets of fault voltages and currents, respectively, i.e.
Figure BDA0002070054280000049
And
Figure BDA00020700542800000410
and
Figure BDA00020700542800000411
(2) and respectively intercepting the voltage transient and the current transient 3ms after the fault according to a second step in the specification and carrying out 8-scale wavelet decomposition on the voltage transient and the current transient.
(3) Selecting wavelet coefficients under the first scale of voltage and current transient states as shown in figures 6 and 7 according to the third step of the specification to carry out correlation analysis, and obtaining two groups of correlation coefficients
Figure BDA00020700542800000412
(4) Correlation coefficient
Figure BDA00020700542800000413
Satisfy the requirement of
Figure BDA00020700542800000414
Correlation coefficient
Figure BDA00020700542800000415
Satisfy the requirement of
Figure BDA00020700542800000416
It can be judged as an in-zone MN leg failure.
Example 4: a 220kV mixed compensation circuit simulation model containing UPFC and fixed series compensation C is shown in FIG. 1; the circuit parameters are as follows: the line length of the PM branch is 100km, the line lengths of the ME branch and the FN branch are both 75km, and the line length of the NQ branch is 120 km. Fault location: the NQ branch has a fault 40km away from the N end. The sampling frequency is 1 MHz. The fixed series compensation C is 20.5 muF. The failure initial time t is 0.17 s.
(1) According to the direction element R at end M, N after the first step of fault occurs in the specification1、R2Obtaining transient quantities of two sets of fault voltages and currents, respectively, i.e.
Figure BDA00020700542800000417
And
Figure BDA00020700542800000418
and
Figure BDA00020700542800000419
(2) and respectively intercepting the voltage transient and the current transient 3ms after the fault according to a second step in the specification and carrying out 8-scale wavelet decomposition on the voltage transient and the current transient.
(3) Selecting wavelet coefficients under the first scale of voltage and current transient states as shown in figures 8 and 9 according to the third step of the specification to carry out correlation analysis, and obtaining two groups of correlation coefficients
Figure BDA0002070054280000051
(4) Correlation coefficient
Figure BDA0002070054280000052
Satisfy the requirement of
Figure BDA0002070054280000053
Correlation coefficient
Figure BDA0002070054280000054
Satisfy the requirement of
Figure BDA0002070054280000055
It may be determined as an out-of-zone NQ branch fault.
While the present invention has been described in detail with reference to the embodiments shown in the drawings, the present invention is not limited to the embodiments, and various changes can be made without departing from the spirit and scope of the present invention.

Claims (1)

1. A UPFC and fixed series compensation C-containing hybrid compensation line protection method based on correlation analysis is characterized by comprising the following steps: when the hybrid compensation line has single-phase earth fault, firstly passes through the direction element R at the end M, N1、R2Obtaining transient quantities of two sets of fault voltages and currents, respectively, i.e.
Figure FDA0003071245870000011
And
Figure FDA0003071245870000012
and
Figure FDA0003071245870000013
secondly, respectively intercepting the voltage and current transient state quantity 3ms after the fault and carrying out 8-scale wavelet decomposition on the voltage and current transient state quantity, then selecting the wavelet coefficient under the first scale to carry out correlation analysis, and solving two groups of correlation coefficients
Figure FDA0003071245870000014
The positive direction of the specified current is the direction of the bus pointing to the line, the internal and external fault criteria of the small wave coefficient correlation construction area under the first scale of the voltage and the current detected at the head end and the tail end are used, if the internal and external fault criteria are not used, the external fault criteria are judged
Figure FDA0003071245870000015
And is
Figure FDA0003071245870000016
The MN section in the area is in failure; if it is
Figure FDA0003071245870000017
And is
Figure FDA0003071245870000018
The PM section fault outside the system area is detected; if it is
Figure FDA0003071245870000019
And is
Figure FDA00030712458700000110
The system area is an NQ section fault;
selecting the wavelet basis function as db 8;
wavelet coefficients under the first scale of voltage and current transient are respectively selected for correlation analysis, and two groups of correlation coefficients r are obtainedu,iComprises the following steps:
Figure FDA00030712458700000111
wherein k is the number of failures of the current transformer on the line connected to the busQuantity, N is the total number of current transformers on the line to which the bus is connected, d1_u(k)、d1_i(k) Wavelet coefficients under a first scale of voltage transient and current transient are respectively;
wherein the content of the first and second substances,
Figure FDA00030712458700000112
respectively representing the voltage and current correlation coefficients of the M side and the N side;
the wavelet coefficient negative correlation under the first scale of the voltage and the current detected by the equivalent measuring end, and the threshold value r of the correlation coefficientset1-0.4; the wavelet coefficient under the first scale of the voltage and the current detected by the equivalent measuring end is positively correlated, and the threshold value r of the correlation coefficientset2＝0.4。
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Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN104393581A (en) * 2014-11-05 2015-03-04 昆明理工大学 Triangle looped network transient state quantity unit protection method utilizing voltage and current abrupt change quantity wavelet coefficient correlation analysis
CN107104420A (en) * 2017-05-22 2017-08-29 华北电力大学 The segment protection method of circuit distance I accessed suitable for THE UPFC

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN104393581A (en) * 2014-11-05 2015-03-04 昆明理工大学 Triangle looped network transient state quantity unit protection method utilizing voltage and current abrupt change quantity wavelet coefficient correlation analysis
CN107104420A (en) * 2017-05-22 2017-08-29 华北电力大学 The segment protection method of circuit distance I accessed suitable for THE UPFC

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
基于波形相关性分析的输电线路暂态保护方法;李泽文等;《电力系统及其自动化学报》;20180831;第30卷(第8期);第44-50页 *

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