CN113437732A - Pilot protection method and system for photovoltaic power generation grid-connected tie line - Google Patents

Pilot protection method and system for photovoltaic power generation grid-connected tie line Download PDF

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Publication number
CN113437732A
CN113437732A CN202111002414.4A CN202111002414A CN113437732A CN 113437732 A CN113437732 A CN 113437732A CN 202111002414 A CN202111002414 A CN 202111002414A CN 113437732 A CN113437732 A CN 113437732A
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tie line
sum
phase
photovoltaic
system side
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CN113437732B (en
Inventor
桂小智
潘本仁
梁振锋
张妍
万勇
王冠南
蒙天赐
周仕豪
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State Grid Corp of China SGCC
Xian University of Technology
Electric Power Research Institute of State Grid Jiangxi Electric Power Co Ltd
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State Grid Corp of China SGCC
Xian University of Technology
Electric Power Research Institute of State Grid Jiangxi Electric Power Co Ltd
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    • 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
    • H02H7/261—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 involving signal transmission between at least two stations
    • H02H7/263—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 involving signal transmission between at least two stations involving transmissions of measured values
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H1/00—Details of emergency protective circuit arrangements
    • H02H1/0092—Details of emergency protective circuit arrangements concerning the data processing means, e.g. expert systems, neural networks

Abstract

The invention discloses a pilot protection method and a pilot protection system for a photovoltaic power generation grid-connected tie line, wherein the method comprises the following steps: judging whether a phase current sudden change in the three phases meets a first condition or whether the zero sequence voltage meets a second condition; if the sudden change of a certain phase current in the three phases meets a first condition or the zero sequence voltage meets a second condition, starting the pilot protection, delaying to select a data window of a preset time period, and respectively calculating the current sum and the voltage sum of the photovoltaic side and the system side of the tie line according to the phases; performing zero sequence compensation on the sum of the voltages of the photovoltaic side and the system side of each connecting line, then obtaining the derivative of the voltage, and calculating the correlation coefficient of each phase based on the sum of the currents of the photovoltaic side and the system side of each connecting line; and comparing the calculated correlation coefficient of each phase with a setting threshold value, and executing corresponding protection action based on the comparison result. The method and the device realize accurate action under the condition that different fault types occur at different fault positions.

Description

Pilot protection method and system for photovoltaic power generation grid-connected tie line
Technical Field
The invention belongs to the technical field of power system relay protection, and particularly relates to a pilot protection method and system for a photovoltaic power generation grid-connected tie line.
Background
The solar energy is clean and pollution-free, is widely distributed and inexhaustible, has unique advantages in development and utilization, and has become a hotspot field of the development of new energy at present. The method is influenced by the self power supply characteristic of the photovoltaic and the inversion control strategy thereof, the fault characteristic of the photovoltaic system is different from that of the traditional synchronous machine system, the protection principle formed on the basis of analyzing the fault characteristic of the traditional synchronous machine can not adapt to the change of the fault characteristic of the system after large-scale centralized photovoltaic access, and the protection performance can be reduced, even refused to operate or wrongly operated, such as longitudinal differential protection.
Therefore, the fault characteristics of the photovoltaic grid-connected system need to be analyzed, and a suitable protection scheme needs to be researched to guarantee safe and stable operation of the power grid, which is also significant for strategic development of the photovoltaic industry.
Disclosure of Invention
The invention aims to provide a method and a system for pilot protection of a photovoltaic power generation grid-connected tie line, which solve the problem that the sensitivity of the existing pilot differential protection in the photovoltaic power generation grid-connected tie line is reduced and even the pilot differential protection is not operated.
In a first aspect, the invention provides a pilot protection method for a photovoltaic power generation grid-connected tie line, which comprises the following steps: responding to three-phase voltage data and three-phase current data acquired by a pilot protection device, and judging whether a phase current break variable in three phases meets a first condition or whether a zero-sequence voltage meets a second condition, wherein the expression of the first condition is as follows:
Figure 875859DEST_PATH_IMAGE001
in the formula (I), wherein,
Figure 842678DEST_PATH_IMAGE002
for the purpose of the rated current, the current,
Figure 974845DEST_PATH_IMAGE003
for a certain amount of the phase current burst,
Figure 394325DEST_PATH_IMAGE004
，
Figure 73568DEST_PATH_IMAGE005
is a phase A, a phase B or a phase C,
Figure 19527DEST_PATH_IMAGE006
is the number of sampling points in one period,
Figure 696496DEST_PATH_IMAGE007
is the maximum value of the unbalance amount of a certain phase current,
Figure 727906DEST_PATH_IMAGE008
，
Figure 461374DEST_PATH_IMAGE009
the serial numbers of the sampling points are shown,
Figure 668364DEST_PATH_IMAGE010
is the first moment
Figure 375289DEST_PATH_IMAGE009
The sum of the currents on the photovoltaic side of each tie line and on the system side of the tie line of the sampling points of the individual,
Figure 97258DEST_PATH_IMAGE011
is the first period of a time
Figure 790407DEST_PATH_IMAGE009
The sum of the currents on the photovoltaic side of each tie line and on the system side of the tie line of the sampling points of the individual,
Figure 710959DEST_PATH_IMAGE012
the first two periods of a certain time
Figure 464151DEST_PATH_IMAGE009
The sum of the currents on the photovoltaic side of each tie line and on the system side of the tie line of the sampling points of the individual,
Figure 174880DEST_PATH_IMAGE013
the first three periods of a certain time
Figure 796355DEST_PATH_IMAGE009
The sum of the currents on the photovoltaic side of each tie line and the system side of the tie line of each sampling point; the expression of the second condition is:
Figure 712358DEST_PATH_IMAGE014
in the formula (I), wherein,
Figure 495506DEST_PATH_IMAGE015
for zero sequence voltage on two sides of the grid-connected tie line,
Figure 192067DEST_PATH_IMAGE016
taking the sample at 0.5V to 1V,
Figure 227019DEST_PATH_IMAGE017
taking 1.2-1.5 as a reliable coefficient,
Figure 886277DEST_PATH_IMAGE018
unbalanced voltage for normal operation; if the sudden change of a certain phase current in the three phases meets a first condition or the zero sequence voltage meets a second condition, controlling a pilot protection device to start pilot protection, selecting a data window of a preset time period based on the pilot protection device in a delayed mode, and respectively calculating the current sum and the voltage sum of the photovoltaic side of the tie line and the system side of the tie line according to the phases; obtaining a derivative of the voltage of the photovoltaic side of each connecting line and the voltage of the system side of each connecting line after zero sequence compensation, and calculating a correlation coefficient of each phase based on the sum of the currents of the photovoltaic side of each connecting line and the system side of each connecting line, wherein the expression of the correlation coefficient of each phase is as follows:
Figure 715693DEST_PATH_IMAGE019
in the formula (I), wherein,
Figure 899549DEST_PATH_IMAGE020
is the correlation coefficient of each phase and is,
Figure 862826DEST_PATH_IMAGE005
is a phase A, a phase B or a phase C,
Figure 487843DEST_PATH_IMAGE021
for the start of a sampling point for a window of data,
Figure 81635DEST_PATH_IMAGE022
the number of the sampling points is,
Figure 785411DEST_PATH_IMAGE023
and
Figure 693324DEST_PATH_IMAGE024
the following were used:
Figure 500743DEST_PATH_IMAGE025
in the formula (I), wherein,
Figure 62174DEST_PATH_IMAGE009
as a sampling pointThe serial number of the serial number,
Figure 892727DEST_PATH_IMAGE026
in order to be the sampling interval of the sample,
Figure 197807DEST_PATH_IMAGE027
is the first moment
Figure 364127DEST_PATH_IMAGE009
The sum of the currents on the photovoltaic side of each tie line and on the system side of the tie line of the sampling points of the individual,
Figure 237405DEST_PATH_IMAGE028
is the first moment
Figure 414308DEST_PATH_IMAGE029
The sum of the currents on the photovoltaic side of each tie line and on the system side of the tie line of the sampling points of the individual,
Figure 460762DEST_PATH_IMAGE030
is the first moment
Figure 914877DEST_PATH_IMAGE029
The sum of the voltages of the photovoltaic side of each connecting line and the system side of the connecting line after zero sequence compensation,
Figure 83690DEST_PATH_IMAGE031
is the first moment
Figure 623256DEST_PATH_IMAGE009
The sum of the voltages of the photovoltaic side and the system side of each tie line after zero sequence compensation of each sampling point; and comparing the calculated correlation coefficient of each phase with a setting threshold value, and executing corresponding protection action based on the comparison result.
In a second aspect, the present invention provides a pilot protection system for a photovoltaic power generation grid-connected tie line, including: a judging module configured to judge a certain phase current among the three phases in response to the three-phase voltage data and the three-phase current data acquired by the pilot protection device being acquiredWhether the break variable meets a first condition or whether the zero sequence voltage meets a second condition, wherein the expression of the first condition is as follows:
Figure 974865DEST_PATH_IMAGE001
in the formula (I), wherein,
Figure 673699DEST_PATH_IMAGE002
for the purpose of the rated current, the current,
Figure 623201DEST_PATH_IMAGE003
for a certain amount of the phase current burst,
Figure 712380DEST_PATH_IMAGE004
，
Figure 162952DEST_PATH_IMAGE005
is a phase A, a phase B or a phase C,
Figure 591660DEST_PATH_IMAGE006
is the number of sampling points in one period,
Figure 804073DEST_PATH_IMAGE007
is the maximum value of the unbalance amount of a certain phase current,
Figure 646127DEST_PATH_IMAGE008
，
Figure 900391DEST_PATH_IMAGE009
the serial numbers of the sampling points are shown,
Figure 245922DEST_PATH_IMAGE010
is the first moment
Figure 68384DEST_PATH_IMAGE009
The sum of the currents on the photovoltaic side of each tie line and on the system side of the tie line of the sampling points of the individual,
Figure 430358DEST_PATH_IMAGE011
is the first period of a time
Figure 425995DEST_PATH_IMAGE009
The sum of the currents on the photovoltaic side of each tie line and on the system side of the tie line of the sampling points of the individual,
Figure 563716DEST_PATH_IMAGE012
the first two periods of a certain time
Figure 416134DEST_PATH_IMAGE009
The sum of the currents on the photovoltaic side of each tie line and on the system side of the tie line of the sampling points of the individual,
Figure 967201DEST_PATH_IMAGE013
the first three periods of a certain time
Figure 173054DEST_PATH_IMAGE009
The sum of the currents on the photovoltaic side of each tie line and the system side of the tie line of each sampling point; the expression of the second condition is:
Figure 48170DEST_PATH_IMAGE014
in the formula (I), wherein,
Figure 946856DEST_PATH_IMAGE015
for zero sequence voltage on two sides of the grid-connected tie line,
Figure 719640DEST_PATH_IMAGE016
taking the sample at 0.5V to 1V,
Figure 853818DEST_PATH_IMAGE017
taking 1.2-1.5 as a reliable coefficient,
Figure 231710DEST_PATH_IMAGE018
unbalanced voltage for normal operation; the first calculation module is configured to control the pilot protection device to start pilot protection if a phase current mutation amount in the three phases meets a first condition or a zero sequence voltage meets a second condition, and select a preset time period based on the pilot protection device delayThe data window of (2) calculates the sum of the current and the sum of the voltage of the photovoltaic side and the system side of the tie line respectively according to the phase; the second calculation module is configured to perform zero sequence compensation on the sum of the voltages of the photovoltaic side and the system side of each tie line, obtain a derivative of the voltage, and calculate each phase correlation coefficient based on the sum of the currents of the photovoltaic side and the system side of each tie line, wherein the expression of each phase correlation coefficient is as follows:
Figure 363614DEST_PATH_IMAGE019
in the formula (I), wherein,
Figure 187476DEST_PATH_IMAGE020
is the correlation coefficient of each phase and is,
Figure 711DEST_PATH_IMAGE005
is a phase A, a phase B or a phase C,
Figure 92164DEST_PATH_IMAGE021
for the start of a sampling point for a window of data,
Figure 863810DEST_PATH_IMAGE022
the number of the sampling points is,
Figure 939083DEST_PATH_IMAGE023
and
Figure 290430DEST_PATH_IMAGE024
the following were used:
Figure 938186DEST_PATH_IMAGE025
in the formula (I), wherein,
Figure 474210DEST_PATH_IMAGE009
the serial numbers of the sampling points are shown,
Figure 646565DEST_PATH_IMAGE026
in order to be the sampling interval of the sample,
Figure 660658DEST_PATH_IMAGE027
is the first moment
Figure 929965DEST_PATH_IMAGE009
The sum of the currents on the photovoltaic side of each tie line and on the system side of the tie line of the sampling points of the individual,
Figure 246677DEST_PATH_IMAGE028
is the first moment
Figure 532427DEST_PATH_IMAGE029
The sum of the currents on the photovoltaic side of each tie line and on the system side of the tie line of the sampling points of the individual,
Figure 225576DEST_PATH_IMAGE030
is the first moment
Figure 349390DEST_PATH_IMAGE029
The sum of the voltages of the photovoltaic side of each connecting line and the system side of the connecting line after zero sequence compensation,
Figure 227216DEST_PATH_IMAGE031
is the first moment
Figure 374164DEST_PATH_IMAGE009
The sum of the voltages of the photovoltaic side and the system side of each tie line after zero sequence compensation of each sampling point; and the execution module is configured to compare the calculated correlation coefficient of each phase with a setting threshold value and execute corresponding protection actions based on the comparison result.
In a third aspect, an electronic device is provided, comprising: the protection method comprises at least one processor and a memory which is in communication connection with the at least one processor, wherein the memory stores instructions executable by the at least one processor, and the instructions are executed by the at least one processor to enable the at least one processor to execute the steps of the photovoltaic grid-connected pilot protection method according to any embodiment of the invention.
In a fourth aspect, the present invention also provides a computer-readable storage medium having stored thereon a computer program comprising program instructions which, when executed by a computer, cause the computer to perform the steps of the method for pv grid tie pilot protection according to any of the embodiments of the present invention.
According to the method and the system for pilot protection of the photovoltaic power generation grid-connected tie line, the derivative of the sum of the currents on the two sides and the sum of the voltages is calculated according to the phases, the correlation coefficient is obtained, whether the grid-connected tie line fault is located in the region or out of the region is judged according to the magnitude between the obtained correlation coefficient and the setting threshold value, the corresponding fault type is judged, the photovoltaic inversion control strategy and the photovoltaic power generation output magnitude are not influenced, accurate action can be achieved under the condition that different fault types occur at different fault positions, the method and the system have strong anti-transition resistance capacity, and the sensitivity and the reliability are high.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on the drawings without creative efforts.
Fig. 1 is a flowchart of a pilot protection method for a photovoltaic power generation grid-connected tie line according to an embodiment of the present invention;
fig. 2 is an equivalent circuit diagram of the photovoltaic power generation grid-connected tie line provided by an embodiment of the present invention when an external fault occurs;
fig. 3 is an equivalent circuit diagram of a fault in a photovoltaic power generation grid-connected tie line area according to an embodiment of the present invention;
fig. 4 is a schematic diagram of a fault simulation of a centralized photovoltaic power generation grid-connected system according to an embodiment of the present invention;
fig. 5 is a block diagram of a pilot protection system of a photovoltaic power generation grid-connected tie line according to an embodiment of the present invention;
fig. 6 is a schematic structural diagram of an electronic device according to an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Referring to fig. 1, a flow chart of a pilot protection method for a photovoltaic power generation grid-connected tie line according to the present application is shown.
As shown in fig. 1, in S101, in response to obtaining three-phase voltage data and three-phase current data collected by a pilot protection device, it is determined whether a phase current break variable in three phases meets a first condition or whether a zero-sequence voltage meets a second condition, where an expression of the first condition is:
Figure 730059DEST_PATH_IMAGE001
in the formula (I), wherein,
Figure 212774DEST_PATH_IMAGE002
for the purpose of the rated current, the current,
Figure 136867DEST_PATH_IMAGE003
for a certain amount of the phase current burst,
Figure 895745DEST_PATH_IMAGE004
，
Figure 258593DEST_PATH_IMAGE005
is a phase A, a phase B or a phase C,
Figure 763524DEST_PATH_IMAGE006
is the number of sampling points in one period,
Figure 451994DEST_PATH_IMAGE007
is the maximum value of the unbalance amount of a certain phase current,
Figure 934053DEST_PATH_IMAGE008
，
Figure 772696DEST_PATH_IMAGE009
the serial numbers of the sampling points are shown,
Figure 725609DEST_PATH_IMAGE010
is the first moment
Figure 116139DEST_PATH_IMAGE009
The sum of the currents on the photovoltaic side of each tie line and on the system side of the tie line of the sampling points of the individual,
Figure 459395DEST_PATH_IMAGE011
is the first period of a time
Figure 226363DEST_PATH_IMAGE009
The sum of the currents on the photovoltaic side of each tie line and on the system side of the tie line of the sampling points of the individual,
Figure 532317DEST_PATH_IMAGE012
the first two periods of a certain time
Figure 234694DEST_PATH_IMAGE009
The sum of the currents on the photovoltaic side of each tie line and on the system side of the tie line of the sampling points of the individual,
Figure 924301DEST_PATH_IMAGE013
the first three periods of a certain time
Figure 167064DEST_PATH_IMAGE009
The sum of the currents on the photovoltaic side of each tie line and the system side of the tie line of each sampling point;
the expression of the second condition is:
Figure 766673DEST_PATH_IMAGE014
in the formula (I), wherein,
Figure 764584DEST_PATH_IMAGE015
for zero sequence voltage on two sides of the grid-connected tie line,
Figure 816854DEST_PATH_IMAGE016
taking the sample at 0.5V to 1V,
Figure 161510DEST_PATH_IMAGE017
taking 1.2-1.5 as a reliable coefficient,
Figure 943521DEST_PATH_IMAGE018
is an unbalanced voltage in normal operation.
In S102, if a phase current sudden change in three phases meets a first condition or a zero sequence voltage meets a second condition, the pilot protection device is controlled to start pilot protection, a data window of a preset time period is selected based on the pilot protection device in a delayed manner, and the sum of the current and the sum of the voltage of the tie line photovoltaic side and the tie line system side are respectively calculated according to the phases.
In this embodiment, after pilot protection is started, a data window of a preset time period is selected in a delayed mode, and the sum of the current and the sum of the voltage of the photovoltaic side of the tie line and the system side of the tie line are calculated according to the phase, so that the data after delay are calculated, and the influence of a control transient on protection is reduced.
In S103, the sum of the voltages on the photovoltaic side and the tie line system side of each tie line is zero-sequence compensated, and then the derivative thereof is obtained, and correlation coefficients of each phase are calculated based on the sum of the currents on the photovoltaic side and the tie line system side of each tie line, wherein the expression of the correlation coefficients of each phase is:
Figure 722121DEST_PATH_IMAGE019
，
in the formula (I), the compound is shown in the specification,
Figure 386321DEST_PATH_IMAGE020
is the correlation coefficient of each phase and is,
Figure 174148DEST_PATH_IMAGE005
is a phase A, a phase B or a phase C,
Figure 607404DEST_PATH_IMAGE021
for the start of a sampling point for a window of data,
Figure 556905DEST_PATH_IMAGE022
the number of the sampling points is,
Figure 162197DEST_PATH_IMAGE023
and
Figure 878349DEST_PATH_IMAGE024
the following were used:
Figure 41477DEST_PATH_IMAGE025
，
in the formula (I), the compound is shown in the specification,
Figure 286514DEST_PATH_IMAGE009
the serial numbers of the sampling points are shown,
Figure 128568DEST_PATH_IMAGE026
in order to be the sampling interval of the sample,
Figure 992619DEST_PATH_IMAGE027
is the first moment
Figure 636352DEST_PATH_IMAGE009
The sum of the currents on the photovoltaic side of each tie line and on the system side of the tie line of the sampling points of the individual,
Figure 193235DEST_PATH_IMAGE028
is the first moment
Figure 319323DEST_PATH_IMAGE029
The sum of the currents on the photovoltaic side of each tie line and on the system side of the tie line of the sampling points of the individual,
Figure 721486DEST_PATH_IMAGE030
is the first moment
Figure 983840DEST_PATH_IMAGE029
The sum of the voltages of the photovoltaic side of each connecting line and the system side of the connecting line after zero sequence compensation,
Figure 711624DEST_PATH_IMAGE031
is the first moment
Figure 997112DEST_PATH_IMAGE009
And the sum of the voltages of the photovoltaic side of each connecting line and the system side of the connecting line after zero sequence compensation of each sampling point.
In this embodiment, the expression for performing zero sequence compensation on the sum of the voltages on the photovoltaic side and the tie line system side of each tie line is as follows:
Figure 91714DEST_PATH_IMAGE032
，
in the formula (I), the compound is shown in the specification,
Figure 83940DEST_PATH_IMAGE033
the sum of the voltages of the photovoltaic side of each connecting line and the system side of the connecting line after zero sequence compensation,
Figure 841681DEST_PATH_IMAGE034
is the sum of the voltages on the photovoltaic side of each tie line and on the system side of the tie line,
Figure 817727DEST_PATH_IMAGE005
is a phase A, a phase B or a phase C,
Figure 951905DEST_PATH_IMAGE035
for zero sequence voltage on two sides of the grid-connected tie line,
Figure 798639DEST_PATH_IMAGE036
is a zero-sequence compensation coefficient, and the zero-sequence compensation coefficient,
Figure 992859DEST_PATH_IMAGE037
are respectively connected to the gridThe zero sequence capacitor of the unit length of the grid-connected tie line and the positive sequence capacitor of the unit length of the grid-connected tie line.
And after carrying out zero sequence compensation on the sum of the voltages of the photovoltaic side and the system side of each connecting line, calculating a derivative of the voltage through a differential derivative method, wherein the expression of the derivative is as follows:
Figure 754404DEST_PATH_IMAGE038
，
in the formula (I), the compound is shown in the specification,
Figure 567640DEST_PATH_IMAGE009
the serial numbers of the sampling points are shown,
Figure 659092DEST_PATH_IMAGE026
in order to be the sampling interval of the sample,
Figure 899581DEST_PATH_IMAGE033
the sum of the voltages of the photovoltaic side of each connecting line and the system side of the connecting line after zero sequence compensation,
Figure 709274DEST_PATH_IMAGE030
is the first moment
Figure 60621DEST_PATH_IMAGE029
The sum of the voltages of the photovoltaic side of each connecting line and the system side of the connecting line after zero sequence compensation,
Figure 209842DEST_PATH_IMAGE031
is the first moment
Figure 984681DEST_PATH_IMAGE009
And the sum of the voltages of the photovoltaic side of each connecting line and the system side of the connecting line after zero sequence compensation of each sampling point.
Further, the correlation coefficient of each phase
Figure 891457DEST_PATH_IMAGE020
Has a value range of [ -1,1 [)]When is coming into contact with
Figure 436708DEST_PATH_IMAGE039
Is shown by
Figure 112540DEST_PATH_IMAGE040
And
Figure 819465DEST_PATH_IMAGE041
negative correlation;
Figure 213537DEST_PATH_IMAGE042
is shown by
Figure 234583DEST_PATH_IMAGE040
And
Figure 656599DEST_PATH_IMAGE041
non-correlation;
Figure 409792DEST_PATH_IMAGE043
is shown by
Figure 150214DEST_PATH_IMAGE040
And
Figure 912634DEST_PATH_IMAGE041
and (4) positively correlating.
Figure 687692DEST_PATH_IMAGE044
The closer the value is to 1, the more the representation
Figure 611786DEST_PATH_IMAGE040
And
Figure 105084DEST_PATH_IMAGE041
the stronger the positive correlation;
Figure 966467DEST_PATH_IMAGE044
the closer the value is to-1, the stronger the negative correlation. When a fault occurs outside the zone, each phase
Figure 471398DEST_PATH_IMAGE040
And
Figure 691027DEST_PATH_IMAGE041
conforms to the capacitance circuit model and shows strong positive correlation,
Figure 546987DEST_PATH_IMAGE044
a value close to 1; when in-zone fault, non-fault phase
Figure 510264DEST_PATH_IMAGE040
And
Figure 135281DEST_PATH_IMAGE041
conforms to the capacitance circuit model and shows strong positive correlation,
Figure 729073DEST_PATH_IMAGE044
the value is close to 1, while the faulted phase does not fit the capacitive circuit model,
Figure 432849DEST_PATH_IMAGE044
the value is less than 1.
In S104, the calculated correlation coefficient of each phase is compared with a setting threshold value, and a corresponding protection operation is executed based on the comparison result.
In this embodiment, comparing the calculated correlation coefficient of each phase with a setting threshold, and executing a corresponding protection action based on the comparison result specifically includes: if the correlation coefficient of one of the three phases is smaller than a setting threshold value, judging that the single-phase fault exists in a photovoltaic power generation grid-connected tie line area, and protecting the action from jumping to the single phase; if the correlation coefficient of a certain two phases is smaller than a setting threshold value or the correlation coefficients of the three phases are smaller than the setting threshold value, judging that two-phase faults and three-phase faults in a grid-connected tie line area exist, and protecting the action from jumping the three phases; if the correlation coefficients of the three phases are all larger than the setting threshold value, the fact that no fault occurs inside the grid-connected tie line is judged, and the protection does not act.
In the method of the embodiment, according to the fact that the derivative of the sum of the currents and the sum of the voltages on the two sides of the photovoltaic power generation grid-connected tie line accords with different circuit models when the photovoltaic power generation grid-connected tie line is in an inside fault and an outside fault, model identification is carried out through correlation analysis so as to judge the fault, when the photovoltaic power generation grid-connected tie line is in the outside fault, the derivative of the sum of the currents on the two sides of each tie line and the derivative of the sum of the voltages on the two sides of each tie line are in strong positive correlation, and the similarity coefficient is close to 1; when the fault occurs in the region, the derivative of the sum of the currents on the two sides of the non-fault phase and the sum of the voltages on the two sides is in strong positive correlation, the similarity coefficient is close to 1, and the similarity coefficient of the derivative of the sum of the currents on the two sides of the fault phase and the sum of the voltages on the two sides is smaller than 1. The invention directly analyzes the correlation by using the derivative of the sum of the voltages at two sides of the connecting line and the sum of the currents, and the algorithm is simple and reliable; the data after the time delay is adopted for calculation, so that the influence of the control transient on the protection is reduced; the photovoltaic inverter control device is not influenced by a photovoltaic inverter control strategy and the output of photovoltaic power generation, can accurately act under the condition that different fault types occur at different fault positions, and has strong anti-transition resistance capability and high reliability and sensitivity.
FIG. 2 is an equivalent circuit diagram of a fault outside a photovoltaic power generation grid-connected line area, wherein a positive direction is defined as a bus flow direction line, a P side is a photovoltaic side,
Figure 809604DEST_PATH_IMAGE045
and
Figure 413760DEST_PATH_IMAGE046
respectively photovoltaic side fault voltage and fault current; the S side is the system side,
Figure 116137DEST_PATH_IMAGE047
and
Figure 805744DEST_PATH_IMAGE048
respectively a system-side fault voltage and a fault current,
Figure 986190DEST_PATH_IMAGE049
is the line impedance of the grid-tie line,
Figure 710432DEST_PATH_IMAGE050
in order to be a line-to-ground capacitance,
Figure 318131DEST_PATH_IMAGE051
in order to connect the out-of-zone fault point,
Figure 925394DEST_PATH_IMAGE052
is the transition resistance of the point of failure,
Figure 34164DEST_PATH_IMAGE053
is the current flowing through the transition resistance. The current relation of two sides of the photovoltaic power generation grid-connected tie line is shown as the formula (1):
Figure 488279DEST_PATH_IMAGE054
（1）
in the formula (I), the compound is shown in the specification,
Figure 657092DEST_PATH_IMAGE046
in order to obtain a photovoltaic side fault current,
Figure 931079DEST_PATH_IMAGE055
for each of the associated tie line photovoltaic side fault currents,
Figure 577961DEST_PATH_IMAGE056
for each of the associated tie line system side fault currents,
Figure 886582DEST_PATH_IMAGE048
in order to be the system-side fault current,
Figure 462182DEST_PATH_IMAGE057
、
Figure 489044DEST_PATH_IMAGE058
respectively, photovoltaic side and system side capacitance-to-ground current.
Figure 877300DEST_PATH_IMAGE059
（2）
In the formula (I), the compound is shown in the specification,
Figure 430641DEST_PATH_IMAGE060
for photovoltaic side fault electricityThe pressure is applied to the inner wall of the cylinder,
Figure 816623DEST_PATH_IMAGE061
in order to be a system-side fault voltage,
Figure 189836DEST_PATH_IMAGE062
in order to be a line-to-ground capacitance,
Figure 53887DEST_PATH_IMAGE063
for the differentiation of the photovoltaic side fault voltage function with respect to time,
Figure 163532DEST_PATH_IMAGE064
differentiation of the system-side fault voltage function with respect to time.
The sum of the currents on the photovoltaic side and the system side of each tie line is
Figure 579470DEST_PATH_IMAGE065
Sum of voltages on the photovoltaic side and the system side of each tie
Figure 315344DEST_PATH_IMAGE066
，
Figure 107720DEST_PATH_IMAGE067
And
Figure 511019DEST_PATH_IMAGE068
the sizes are equal and the directions are opposite,
Figure 97859DEST_PATH_IMAGE069
，
the following can be obtained from formula (1) and formula (2):
Figure 321029DEST_PATH_IMAGE070
（3）
as shown in formula (3), the derivative of the sum of the currents on both sides of the tie line and the sum of the voltages on both sides of the tie line conforms to the capacitance circuit model and is in strong positive correlation.
Fig. 3 is a fault equivalent circuit diagram in a photovoltaic power generation grid-connected tie line area. The positive direction is defined as the bus flow to the line. And when the fault occurs in the area, the voltages at two sides of the line meet the following conditions:
Figure 418561DEST_PATH_IMAGE071
（4）
in the formula (I), the compound is shown in the specification,
Figure 738684DEST_PATH_IMAGE060
in order to obtain a photovoltaic side fault voltage,
Figure 371790DEST_PATH_IMAGE061
in order to be a system-side fault voltage,
Figure 206891DEST_PATH_IMAGE072
respectively a photovoltaic side resistance value and an inductance value of the connecting line,
Figure 216435DEST_PATH_IMAGE073
for each of the associated tie line photovoltaic side fault currents,
Figure 453382DEST_PATH_IMAGE074
for each of the associated tie line system side fault currents,
Figure 522969DEST_PATH_IMAGE075
is the transition resistance of the point of failure,
Figure 349760DEST_PATH_IMAGE076
is the current flowing through the transition resistance and,
Figure 287629DEST_PATH_IMAGE077
the resistance value and the inductance value of the tie line system are respectively.
Neglecting the capacitance current to ground, the sum of the currents on both sides of the tie line and the sum of the voltages on both sides are shown as formula (5):
Figure 254448DEST_PATH_IMAGE078
（5）
in the formula (I), the compound is shown in the specification,
Figure 619571DEST_PATH_IMAGE073
for each of the associated tie line photovoltaic side fault currents,
Figure 39051DEST_PATH_IMAGE074
for each of the associated tie line system side fault currents,
Figure 219759DEST_PATH_IMAGE079
is the sum of the currents on the photovoltaic side and the tie system side of each tie,
Figure 165718DEST_PATH_IMAGE080
is the sum of the voltages on the photovoltaic side of each tie line and on the system side of the tie line.
Current flowing through the transition resistance in the event of an in-zone fault
Figure 577108DEST_PATH_IMAGE081
Let the current distribution coefficient be
Figure 874097DEST_PATH_IMAGE082
，
Figure 29135DEST_PATH_IMAGE083
From formulas (4) and (5), it is possible to obtain:
Figure 829600DEST_PATH_IMAGE084
（6）
in the formula (I), the compound is shown in the specification,
Figure 411891DEST_PATH_IMAGE080
is the sum of the voltages on the photovoltaic side of each tie line and on the system side of the tie line,
Figure 632395DEST_PATH_IMAGE085
in order to obtain the photovoltaic side resistance value of the tie line,
Figure 450178DEST_PATH_IMAGE086
in order to obtain a tie line system-side resistance value,
Figure 246096DEST_PATH_IMAGE087
for the value of the photovoltaic side inductance of the tie line,
Figure 858343DEST_PATH_IMAGE088
for the value of the inductance on the system side of the tie line,
Figure 5290DEST_PATH_IMAGE082
for the current distribution coefficient of the photovoltaic side,
Figure 626765DEST_PATH_IMAGE089
the coefficient is distributed to the system-side current,
Figure 277189DEST_PATH_IMAGE079
is the sum of the currents on the photovoltaic side and the tie system side of each tie,
Figure 827381DEST_PATH_IMAGE075
is the transition resistance of the fault point.
Further, it is possible to obtain:
Figure 258362DEST_PATH_IMAGE090
（7）
wherein:
Figure 293314DEST_PATH_IMAGE091
（8）
in the formula (I), the compound is shown in the specification,
Figure 188458DEST_PATH_IMAGE092
is the sum of the resistances at the two sides of the connecting line,
Figure 283453DEST_PATH_IMAGE093
is the sum of inductances on both sides of the tie line,
Figure 264047DEST_PATH_IMAGE082
for the current distribution coefficient of the photovoltaic side,
Figure 102690DEST_PATH_IMAGE089
the coefficient is distributed to the system-side current,
Figure 368454DEST_PATH_IMAGE094
in order to obtain the photovoltaic side resistance value of the tie line,
Figure 962246DEST_PATH_IMAGE095
in order to obtain a tie line system-side resistance value,
Figure 305503DEST_PATH_IMAGE096
for the value of the photovoltaic side inductance of the tie line,
Figure 806891DEST_PATH_IMAGE097
is the system-side inductance value of the tie line.
As can be seen from equation (7), when a fault occurs in the interconnection zone, the derivative of the sum of the currents and the sum of the voltages on both sides does not conform to the capacitance circuit model.
The implementation process and effect of the photovoltaic power generation grid-connected tie line pilot protection method of the present application are explained in detail with specific embodiments, and fig. 4 is a schematic diagram of fault simulation of a centralized photovoltaic power generation grid-connected system according to an embodiment of the present invention.
The rated capacity of photovoltaic power generation is 150MW, the box transformer substation adopts Dyn wiring, and the rated voltage is 0.69kV/35 kV; the main transformer adopts YNd wiring, the rated voltage is 35kV/220kV, and the rated capacity is 160 MW. The length of the grid-connected connecting line is 40km, the unit positive sequence impedance is 0.076+ j0.338 omega/km, and the unit zero sequence impedance is 0.284+ j0.824 omega/km. The equivalent positive sequence impedance of the external system is 0.4+ j12.568 omega, and the equivalent zero sequence impedance is 0.6+18.849 omega/km. The photovoltaic side and system side protection devices collect data of the photovoltaic side and transmit the data to the opposite end in real time, and the protection devices calculate correlation coefficients to judge faults and send action instructions. The simulation time length is 3s, and the sampling frequency is 2.5 kHz.
Figure 286414DEST_PATH_IMAGE098
Is a photovoltaic sideOutside the zone(s) of the reaction(s),
Figure 847846DEST_PATH_IMAGE099
is an inner outlet of the photovoltaic side area,
Figure 242180DEST_PATH_IMAGE100
is the middle point of the connecting line,
Figure 422626DEST_PATH_IMAGE101
is an outlet in the side area of the system,
Figure 146868DEST_PATH_IMAGE102
outside the system side region
Figure 754567DEST_PATH_IMAGE103
And respectively setting a metallic fault and a belt transition resistance fault, and calculating a correlation coefficient.
Figure 931470DEST_PATH_IMAGE104
Respectively representing the correlation coefficients of A, B, C three phases "
Figure 915607DEST_PATH_IMAGE105
"indicates a protection action and" - "indicates a protection does not. The simulation results of three-phase faults of different fault positions of the photovoltaic power generation grid-connected tie line are directly calculated by taking 5ms and 10ms data windows after the starting element acts are respectively shown in the table 1 and the table 2; table 3 shows simulation results of different types of faults occurring at different positions of the tie line; table 4 shows simulation results of phase a transition resistance ground faults at different fault positions of the tie line; table 5 shows the tie line midpoints under different photovoltaic power generation output conditions
Figure 432039DEST_PATH_IMAGE100
Simulation results of different types of faults are generated; tables 3, 4 and 5 are the results of 10ms delay after starting the element action and then taking the 5ms data window for calculation.
Figure 833808DEST_PATH_IMAGE106
Figure 373374DEST_PATH_IMAGE107
Figure 20256DEST_PATH_IMAGE108
Figure 594457DEST_PATH_IMAGE109
Figure 668592DEST_PATH_IMAGE110
Figure 695454DEST_PATH_IMAGE111
Simulation results in tables 1 and 2 show that when three phases outside the system side area fail, 5ms and 10ms data windows are directly taken for calculation, the similarity coefficients of the B phase are all smaller than 0.85, and misjudgment occurs; the simulation results in tables 3, 4 and 5 show that when the time delay is 10ms after the element is started, and then the data window of 5ms is taken for calculation, the method can reliably judge different types of faults at different positions on the photovoltaic power generation grid-connected connecting line, is not influenced by the magnitude of the output of photovoltaic power generation, and has strong resistance to transition resistance, high sensitivity and reliability.
Referring to fig. 5, a block diagram of a pilot protection system of a photovoltaic power generation grid-connected tie line according to the present application is shown.
As shown in fig. 5, the pv grid-connected tie-line pilot protection system 200 includes a determining module 210, a first calculating module 220, a second calculating module 230, and an executing module 240.
The determining module 210 is configured to determine a phase current sudden change amount in three phases in response to obtaining three-phase voltage data and three-phase current data collected by the pilot protection deviceWhether a first condition is met or whether the zero sequence voltage meets a second condition, wherein an expression of the first condition is as follows:
Figure 83710DEST_PATH_IMAGE112
in the formula (I), wherein,
Figure 872936DEST_PATH_IMAGE113
for a certain amount of the phase current burst,
Figure 258918DEST_PATH_IMAGE114
，
Figure 632131DEST_PATH_IMAGE115
is a phase A, a phase B or a phase C,
Figure 761761DEST_PATH_IMAGE116
is the number of sampling points in one period,
Figure 169609DEST_PATH_IMAGE117
is the maximum value of the unbalance amount of a certain phase current,
Figure 460913DEST_PATH_IMAGE118
，
Figure 321421DEST_PATH_IMAGE119
the serial numbers of the sampling points are shown,
Figure 989163DEST_PATH_IMAGE010
is the first moment
Figure 959174DEST_PATH_IMAGE009
The sum of the currents on the photovoltaic side and the tie-line system side of the sampling points of the individual,
Figure 546013DEST_PATH_IMAGE011
is the first period of a time
Figure 34763DEST_PATH_IMAGE009
Photovoltaic side and tie line system of sampling point of individualThe sum of the currents of the sides is,
Figure 365250DEST_PATH_IMAGE012
the first two periods of a certain time
Figure 357477DEST_PATH_IMAGE009
The sum of the currents on the photovoltaic side and the tie-line system side of the sampling points of the individual,
Figure 584059DEST_PATH_IMAGE013
the first three periods of a certain time
Figure 920625DEST_PATH_IMAGE009
The sum of the currents on the photovoltaic side and the tie line system side of the sampling points of the individual;
the expression of the second condition is:
Figure 664590DEST_PATH_IMAGE120
in the formula (I), wherein,
Figure 901536DEST_PATH_IMAGE121
for zero sequence voltage on two sides of the grid-connected tie line,
Figure 971123DEST_PATH_IMAGE122
taking the sample at 0.5V to 1V,
Figure 293520DEST_PATH_IMAGE123
taking 1.2-1.5 as a reliable coefficient,
Figure 841176DEST_PATH_IMAGE124
unbalanced voltage for normal operation;
the first calculation module 220 is configured to control the pilot protection device to start pilot protection if a certain phase current mutation in the three phases meets a first condition or zero-sequence voltage meets a second condition, select a data window of a preset time period based on the pilot protection device in a delayed manner, and calculate the sum of the current and the sum of the voltage of the tie line photovoltaic side and the tie line system side respectively according to the phases;
the second calculating module 230 is configured to perform zero sequence compensation on the sum of the voltages at the photovoltaic side and the system side of each tie line, obtain a derivative thereof, and calculate a correlation coefficient of each phase based on the sum of the currents at the photovoltaic side and the system side of each tie line, where an expression of the correlation coefficient of each phase is:
Figure 932629DEST_PATH_IMAGE125
，
in the formula (I), the compound is shown in the specification,
Figure 999549DEST_PATH_IMAGE126
is the correlation coefficient of each phase and is,
Figure 419029DEST_PATH_IMAGE115
is a phase A, a phase B or a phase C,
Figure 895010DEST_PATH_IMAGE127
for the start of a sampling point for a window of data,
Figure 981914DEST_PATH_IMAGE128
the number of the sampling points is,
Figure 517938DEST_PATH_IMAGE129
and
Figure 424714DEST_PATH_IMAGE130
the following were used:
Figure 642069DEST_PATH_IMAGE131
，
in the formula (I), the compound is shown in the specification,
Figure 209578DEST_PATH_IMAGE009
the serial numbers of the sampling points are shown,
Figure 791870DEST_PATH_IMAGE026
in order to be the sampling interval of the sample,
Figure 310576DEST_PATH_IMAGE027
is the first moment
Figure 269304DEST_PATH_IMAGE009
The sum of the currents on the photovoltaic side and the tie-line system side of the sampling points of the individual,
Figure 924277DEST_PATH_IMAGE028
is the first moment
Figure 677469DEST_PATH_IMAGE029
The sum of the currents on the photovoltaic side and the tie-line system side of the sampling points of the individual,
Figure 683471DEST_PATH_IMAGE030
is the first moment
Figure 180311DEST_PATH_IMAGE029
The sum of the voltages of the photovoltaic side and the tie line system side after zero sequence compensation of the photovoltaic grid-connected inverter,
Figure 651308DEST_PATH_IMAGE031
is the first moment
Figure 434456DEST_PATH_IMAGE009
The sum of the voltages of the photovoltaic side and the tie line system side of the sampling points after zero sequence compensation;
and the execution module 240 is configured to compare the calculated correlation coefficient of each phase with a setting threshold value, and execute a corresponding protection action based on the comparison result.
It should be understood that the modules recited in fig. 5 correspond to various steps in the method described with reference to fig. 1. Thus, the operations and features described above for the method and the corresponding technical effects are also applicable to the modules in fig. 5, and are not described again here.
In other embodiments, the present invention further provides a computer-readable storage medium, where computer-executable instructions are stored, where the computer-executable instructions may execute the method for pilot protection of a photovoltaic power generation grid-connected tie line in any of the above method embodiments;
as one embodiment, the computer-readable storage medium of the present invention stores computer-executable instructions configured to:
responding to the three-phase voltage data and the three-phase current data acquired by the pilot protection device, and judging whether a certain phase current break variable in the three phases meets a first condition or whether zero-sequence voltage meets a second condition;
if the sudden change of a certain phase current in the three phases meets a first condition or the zero sequence voltage meets a second condition, controlling a pilot protection device to start pilot protection, selecting a data window of a preset time period based on the pilot protection device in a delayed mode, and respectively calculating the current sum and the voltage sum of the photovoltaic side of the tie line and the system side of the tie line according to the phases;
performing zero sequence compensation on the sum of the voltages of the photovoltaic side and the system side of each connecting line, then obtaining the derivative of the voltage, and calculating the correlation coefficient of each phase based on the sum of the currents of the photovoltaic side and the system side of each connecting line;
and comparing the calculated correlation coefficient of each phase with a setting threshold value, and executing corresponding protection action based on the comparison result.
The computer-readable storage medium may include a storage program area and a storage data area, wherein the storage program area may store an operating system, an application program required for at least one function; the storage data area may store data created from use of the photovoltaic power generation grid-connected tie line pilot protection system, and the like. Further, the computer-readable storage medium may include high speed random access memory, and may also include memory, such as at least one magnetic disk storage device, flash memory device, or other non-volatile solid state storage device. In some embodiments, the computer readable storage medium optionally includes memory remotely located from the processor, and the remote memory may be connected to the pv tie pilot protection system via a network. Examples of such networks include, but are not limited to, the internet, intranets, local area networks, mobile communication networks, and combinations thereof.
Fig. 6 is a schematic structural diagram of an electronic device according to an embodiment of the present invention, and as shown in fig. 6, the electronic device includes: a processor 310 and a memory 320. The electronic device may further include: an input device 330 and an output device 340. The processor 310, the memory 320, the input device 330, and the output device 340 may be connected by a bus or other means, such as the bus connection in fig. 6. The memory 320 is the computer-readable storage medium described above. The processor 310 executes various functional applications and data processing of the server by running the nonvolatile software program, instructions and modules stored in the memory 320, that is, the method for protecting the pilot of the photovoltaic power generation grid-connected tie line according to the embodiment of the method is implemented. The input device 330 may receive input numeric or character information and generate key signal inputs related to user settings and function control of the pv grid tie pilot protection system. The output device 340 may include a display device such as a display screen.
The electronic device can execute the method provided by the embodiment of the invention, and has the corresponding functional modules and beneficial effects of the execution method. For technical details that are not described in detail in this embodiment, reference may be made to the method provided by the embodiment of the present invention.
As an embodiment, the electronic device is applied to a pilot protection system of a photovoltaic power generation grid-connected tie line, and used for a client, and includes: at least one processor; and a memory communicatively coupled to the at least one processor; wherein the memory stores instructions executable by the at least one processor to cause the at least one processor to:
responding to the three-phase voltage data and the three-phase current data acquired by the pilot protection device, and judging whether a certain phase current break variable in the three phases meets a first condition or whether zero-sequence voltage meets a second condition;
if the sudden change of a certain phase current in the three phases meets a first condition or the zero sequence voltage meets a second condition, controlling a pilot protection device to start pilot protection, selecting a data window of a preset time period based on the pilot protection device in a delayed mode, and respectively calculating the current sum and the voltage sum of the photovoltaic side of the tie line and the system side of the tie line according to the phases;
performing zero sequence compensation on the sum of the voltages of the photovoltaic side and the system side of each connecting line, then obtaining the derivative of the voltage, and calculating the correlation coefficient of each phase based on the sum of the currents of the photovoltaic side and the system side of each connecting line;
and comparing the calculated correlation coefficient of each phase with a setting threshold value, and executing corresponding protection action based on the comparison result.
The above-described embodiments of the apparatus are merely illustrative, and the units described as separate parts may or may not be physically separate, and the parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of the present embodiment. One of ordinary skill in the art can understand and implement it without inventive effort.
Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.

Claims (8)

1. A pilot protection method for a photovoltaic power generation grid-connected tie line is characterized by comprising the following steps:
responding to three-phase voltage data and three-phase current data acquired by a pilot protection device, and judging whether a phase current break variable in three phases meets a first condition or whether a zero-sequence voltage meets a second condition, wherein the expression of the first condition is as follows:
Figure 905429DEST_PATH_IMAGE001
in the formula (I), wherein,
Figure 115831DEST_PATH_IMAGE002
for the purpose of the rated current, the current,
Figure 796211DEST_PATH_IMAGE003
for a certain amount of the phase current burst,
Figure 66655DEST_PATH_IMAGE004
，
Figure 973431DEST_PATH_IMAGE005
is a phase A, a phase B or a phase C,
Figure 987524DEST_PATH_IMAGE006
is the number of sampling points in one period,
Figure 663356DEST_PATH_IMAGE007
is the maximum value of the unbalance amount of a certain phase current,
Figure 104701DEST_PATH_IMAGE008
，
Figure 623407DEST_PATH_IMAGE009
the serial numbers of the sampling points are shown,
Figure 50978DEST_PATH_IMAGE010
is the first moment
Figure 697161DEST_PATH_IMAGE009
The sum of the currents on the photovoltaic side of each tie line and on the system side of the tie line of the sampling points of the individual,
Figure 309408DEST_PATH_IMAGE011
is the first period of a time
Figure 925197DEST_PATH_IMAGE009
OfThe sum of the currents on the photovoltaic side and the system side of each tie line at the sampling points,
Figure 546671DEST_PATH_IMAGE012
the first two periods of a certain time
Figure 56150DEST_PATH_IMAGE009
The sum of the currents on the photovoltaic side of each tie line and on the system side of the tie line of the sampling points of the individual,
Figure 714664DEST_PATH_IMAGE013
the first three periods of a certain time
Figure 676804DEST_PATH_IMAGE009
The sum of the currents on the photovoltaic side of each tie line and the system side of the tie line of each sampling point;
the expression of the second condition is:
Figure 836390DEST_PATH_IMAGE014
in the formula (I), wherein,
Figure 341321DEST_PATH_IMAGE015
for zero sequence voltage on two sides of the grid-connected tie line,
Figure 560949DEST_PATH_IMAGE016
taking the sample at 0.5V to 1V,
Figure 10385DEST_PATH_IMAGE017
taking 1.2-1.5 as a reliable coefficient,
Figure 849028DEST_PATH_IMAGE019
unbalanced voltage for normal operation;
if the sudden change of a certain phase current in the three phases meets a first condition or the zero sequence voltage meets a second condition, controlling a pilot protection device to start pilot protection, selecting a data window of a preset time period based on the pilot protection device in a delayed mode, and respectively calculating the current sum and the voltage sum of the photovoltaic side of the tie line and the system side of the tie line according to the phases;
obtaining a derivative of the voltage of the photovoltaic side of each connecting line and the voltage of the system side of each connecting line after zero sequence compensation, and calculating a correlation coefficient of each phase based on the sum of the currents of the photovoltaic side of each connecting line and the system side of each connecting line, wherein the expression of the correlation coefficient of each phase is as follows:
Figure 336029DEST_PATH_IMAGE020
，
in the formula (I), the compound is shown in the specification,
Figure 601925DEST_PATH_IMAGE021
is the correlation coefficient of each phase and is,
Figure 538657DEST_PATH_IMAGE005
is a phase A, a phase B or a phase C,
Figure 40046DEST_PATH_IMAGE022
for the start of a sampling point for a window of data,
Figure 253989DEST_PATH_IMAGE023
the number of the sampling points is,
Figure 549842DEST_PATH_IMAGE024
and
Figure 239449DEST_PATH_IMAGE025
the following were used:
Figure 154315DEST_PATH_IMAGE026
，
in the formula (I), the compound is shown in the specification,
Figure 612978DEST_PATH_IMAGE009
the serial numbers of the sampling points are shown,
Figure 79732DEST_PATH_IMAGE028
in order to be the sampling interval of the sample,
Figure 132001DEST_PATH_IMAGE029
is the first moment
Figure 975193DEST_PATH_IMAGE009
The sum of the currents on the photovoltaic side of each tie line and on the system side of the tie line of the sampling points of the individual,
Figure 163728DEST_PATH_IMAGE030
is the first moment
Figure 804313DEST_PATH_IMAGE031
The sum of the currents on the photovoltaic side of each tie line and on the system side of the tie line of the sampling points of the individual,
Figure 468512DEST_PATH_IMAGE032
is the first moment
Figure 725181DEST_PATH_IMAGE031
The sum of the voltages of the photovoltaic side of each connecting line and the system side of the connecting line after zero sequence compensation,
Figure 158437DEST_PATH_IMAGE033
is the first moment
Figure 966993DEST_PATH_IMAGE009
The sum of the voltages of the photovoltaic side and the system side of each tie line after zero sequence compensation of each sampling point;
and comparing the calculated correlation coefficient of each phase with a setting threshold value, and executing corresponding protection action based on the comparison result.
2. The grid-connected tie line pilot protection method for photovoltaic power generation according to claim 1, wherein the expression for performing zero sequence compensation on the sum of the voltages of the photovoltaic side and the tie line system side of each tie line is as follows:
Figure 993855DEST_PATH_IMAGE034
，
in the formula (I), the compound is shown in the specification,
Figure 178848DEST_PATH_IMAGE036
the sum of the voltages of the photovoltaic side of each connecting line and the system side of the connecting line after zero sequence compensation,
Figure 76397DEST_PATH_IMAGE037
is the sum of the voltages on the photovoltaic side of each tie line and on the system side of the tie line,
Figure 587013DEST_PATH_IMAGE005
is a phase A, a phase B or a phase C,
Figure 694646DEST_PATH_IMAGE038
for zero sequence voltage on two sides of the grid-connected tie line,
Figure 558697DEST_PATH_IMAGE039
is a zero-sequence compensation coefficient, and the zero-sequence compensation coefficient,
Figure 700965DEST_PATH_IMAGE040
the zero sequence capacitor is a grid-connected tie line unit length zero sequence capacitor, and the grid-connected tie line unit length positive sequence capacitor.
3. The method for the pilot protection of the grid-connected photovoltaic power generation tie line according to claim 1, wherein the step of calculating the derivative of the sum of the voltages at the photovoltaic side and the tie line system side of each tie line after zero sequence compensation comprises the steps of:
and after carrying out zero sequence compensation on the sum of the voltages of the photovoltaic side and the system side of each connecting line, calculating a derivative of the voltage through a differential derivative method, wherein the expression of calculating the derivative is as follows:
Figure 323095DEST_PATH_IMAGE041
，
in the formula (I), the compound is shown in the specification,
Figure 918025DEST_PATH_IMAGE009
the serial numbers of the sampling points are shown,
Figure 585766DEST_PATH_IMAGE028
in order to be the sampling interval of the sample,
Figure 848120DEST_PATH_IMAGE036
the sum of the voltages of the photovoltaic side of each connecting line and the system side of the connecting line after zero sequence compensation,
Figure 169380DEST_PATH_IMAGE032
is the first moment
Figure 392551DEST_PATH_IMAGE031
The sum of the voltages of the photovoltaic side and the tie line system side after zero sequence compensation of the photovoltaic grid-connected inverter,
Figure 457459DEST_PATH_IMAGE033
is the first moment
Figure 449686DEST_PATH_IMAGE009
And the sum of the voltages of the photovoltaic side and the tie line system side after zero sequence compensation of the sampling points.
4. The method for pilot protection of the grid-connected tie line for photovoltaic power generation according to claim 1, wherein the setting rule of the setting threshold value is as follows: and (4) considering the sensing error of the mutual inductor, and obtaining the sensing error based on simulation training.
5. The method according to claim 1, wherein the performing of the corresponding protection action based on the comparison result comprises:
if the correlation coefficient of one of the three phases is smaller than a setting threshold value, judging that the single-phase fault exists in a photovoltaic power generation grid-connected tie line area, and protecting the action from jumping to the single phase;
if the correlation coefficient of a certain two phases is smaller than a setting threshold value or the correlation coefficients of the three phases are smaller than the setting threshold value, judging that two-phase faults and three-phase faults in a grid-connected tie line area exist, and protecting the action from jumping the three phases;
if the correlation coefficients of the three phases are all larger than the setting threshold value, the fact that no fault occurs inside the grid-connected tie line is judged, and the protection does not act.
6. The utility model provides a photovoltaic power generation tie-in line pilot protection system that is incorporated into power networks which characterized in that includes:
the judging module is configured to respond to three-phase voltage data and three-phase current data acquired by the pilot protection device, and judge whether a phase current break variable in three phases meets a first condition or whether a zero-sequence voltage meets a second condition, wherein an expression of the first condition is as follows:
Figure 207426DEST_PATH_IMAGE001
in the formula (I), wherein,
Figure 42527DEST_PATH_IMAGE002
for the purpose of the rated current, the current,
Figure 520913DEST_PATH_IMAGE003
for a certain amount of the phase current burst,
Figure 757859DEST_PATH_IMAGE004
，
Figure 435570DEST_PATH_IMAGE005
is a phase A, a phase B or a phase C,
Figure 633334DEST_PATH_IMAGE006
is the number of sampling points in one period,
Figure 305623DEST_PATH_IMAGE007
is the maximum value of the unbalance amount of a certain phase current,
Figure 6863DEST_PATH_IMAGE008
，
Figure 434302DEST_PATH_IMAGE009
the serial numbers of the sampling points are shown,
Figure 775154DEST_PATH_IMAGE010
is the first moment
Figure 719976DEST_PATH_IMAGE009
The sum of the currents on the photovoltaic side of each tie line and on the system side of the tie line of the sampling points of the individual,
Figure 275722DEST_PATH_IMAGE011
is the first period of a time
Figure 280587DEST_PATH_IMAGE009
The sum of the currents on the photovoltaic side of each tie line and on the system side of the tie line of the sampling points of the individual,
Figure 783768DEST_PATH_IMAGE012
the first two periods of a certain time
Figure 125757DEST_PATH_IMAGE009
The sum of the currents on the photovoltaic side of each tie line and on the system side of the tie line of the sampling points of the individual,
Figure 660644DEST_PATH_IMAGE013
the first three periods of a certain time
Figure 977355DEST_PATH_IMAGE009
The sum of the currents on the photovoltaic side of each tie line and the system side of the tie line of each sampling point;
the expression of the second condition is:
Figure 964903DEST_PATH_IMAGE014
in the formula (I), wherein,
Figure 517107DEST_PATH_IMAGE015
for zero sequence voltage on two sides of the grid-connected tie line,
Figure 172079DEST_PATH_IMAGE016
taking the sample at 0.5V to 1V,
Figure 659692DEST_PATH_IMAGE017
taking 1.2-1.5 as a reliable coefficient,
Figure 400115DEST_PATH_IMAGE019
unbalanced voltage for normal operation;
the first calculation module is configured to control the pilot protection device to start pilot protection if a certain phase current mutation in the three phases meets a first condition or zero-sequence voltage meets a second condition, select a data window of a preset time period based on the pilot protection device in a delayed mode, and calculate the sum of the current and the sum of the voltage of the tie line photovoltaic side and the tie line system side respectively according to the phases;
the second calculation module is configured to perform zero sequence compensation on the sum of the voltages of the photovoltaic side and the system side of each tie line, obtain a derivative of the voltage, and calculate each phase correlation coefficient based on the sum of the currents of the photovoltaic side and the system side of each tie line, wherein the expression of each phase correlation coefficient is as follows:
Figure 24519DEST_PATH_IMAGE020
，
in the formula (I), the compound is shown in the specification,
Figure 409364DEST_PATH_IMAGE021
is the correlation coefficient of each phase and is,
Figure 926933DEST_PATH_IMAGE005
is a phase A, a phase B or a phase C,
Figure 154652DEST_PATH_IMAGE022
for the start of a sampling point for a window of data,
Figure 783080DEST_PATH_IMAGE023
the number of the sampling points is,
Figure 412644DEST_PATH_IMAGE024
and
Figure 976481DEST_PATH_IMAGE025
the following were used:
Figure 691496DEST_PATH_IMAGE026
，
in the formula (I), the compound is shown in the specification,
Figure 123614DEST_PATH_IMAGE009
the serial numbers of the sampling points are shown,
Figure 342106DEST_PATH_IMAGE028
in order to be the sampling interval of the sample,
Figure 469986DEST_PATH_IMAGE029
is the first moment
Figure 282085DEST_PATH_IMAGE009
The sum of the currents on the photovoltaic side of each tie line and on the system side of the tie line of the sampling points of the individual,
Figure 783473DEST_PATH_IMAGE030
is the first moment
Figure 387630DEST_PATH_IMAGE031
The sum of the currents on the photovoltaic side of each tie line and on the system side of the tie line of the sampling points of the individual,
Figure 558848DEST_PATH_IMAGE032
is the first moment
Figure 982876DEST_PATH_IMAGE031
The sum of the voltages of the photovoltaic side of each connecting line and the system side of the connecting line after zero sequence compensation,
Figure 22376DEST_PATH_IMAGE033
is the first moment
Figure 215460DEST_PATH_IMAGE009
The sum of the voltages of the photovoltaic side and the system side of each tie line after zero sequence compensation of each sampling point;
and the execution module is configured to compare the calculated correlation coefficient of each phase with a setting threshold value and execute corresponding protection actions based on the comparison result.
7. An electronic device, comprising: at least one processor, and a memory communicatively coupled to the at least one processor, wherein the memory stores instructions executable by the at least one processor to enable the at least one processor to perform the method of any of claims 1 to 5.
8. A computer-readable storage medium, on which a computer program is stored, which, when being executed by a processor, carries out the method of any one of claims 1 to 5.
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