CN111722053A - Multi-energy complementary micro-grid fault rapid identification method and system - Google Patents
Multi-energy complementary micro-grid fault rapid identification method and system Download PDFInfo
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Abstract
The invention relates to a method and a system for rapidly identifying faults of a multi-energy complementary microgrid, wherein the method comprises the following steps: firstly, determining a voltage mismatching value of each line in the microgrid based on a voltage sampling value of each line in the microgrid after a fault occurs; secondly, judging a fault line according to the voltage mismatching value of each line in the microgrid and the sum of three-phase currents; and finally, identifying the fault by using the voltage mismatching value of the fault line and/or the operation parameters before and after the fault. The technical scheme provided by the invention can quickly judge the microgrid fault line and quickly and accurately identify the microgrid fault.
Description
Technical Field
The invention relates to the field of power grid fault identification, in particular to a method and a system for quickly identifying a multi-energy complementary micro-power grid fault.
Background
In recent years, various types of distributed power sources have begun to have access to power distribution networks in large numbers. However, the intermittent and random nature of wind energy, light energy and wave energy makes various distributed power supplies unable to guarantee the stability of output, and when the distributed power supplies were incorporated into the distribution network system on a large scale, how to guarantee the distribution network system source, the load power balance and realize that the system operates steadily became the problem that needs to be solved urgently. In order to improve the reasonable utilization rate of the distributed power supply and realize effective regulation, the micro-grid technology becomes the focus of attention in the industry. At present, a plurality of characteristic micro-grid demonstration projects are built worldwide, and the micro-grids can scientifically configure and regulate and control power generation and energy storage units such as wind power, photovoltaic and wave energy in the grid, so that the purposes of multi-energy complementation and source and load balance are achieved in the grid.
However, due to the fact that a large number of distributed power sources are connected, and the fault characteristics of the micro-grid are obviously different from those of a traditional distribution network under the on-grid/off-grid condition, the traditional relay protection method has many problems in solving the fault protection problem of the micro-grid. Due to the fact that the distributed power supply is incorporated into the original single power supply radiation structure of the system, the tidal current in the microgrid is caused to have a bidirectional flow characteristic, the limited current function of the distributed power supply inverter can control the short-circuit current to be 1.5-2 times of the rated output current, and certain randomness exists in switching-in/switching-out of the small-capacity distributed power supply, and therefore the difficulty of microgrid fault identification and relay protection is increased.
The existing microgrid fault identification method is mainly based on a pattern identification technology, and because the method needs a large number of training samples and test samples, the identification process is complex, and the requirement of relay protection on the quick action performance is not easy to meet.
Disclosure of Invention
Aiming at the defects of the prior art, the invention aims to provide a method and a system for rapidly identifying faults of a multi-energy complementary microgrid, and the method and the system can rapidly identify lines with faults of the microgrid and carry out specific fault identification on the faulty lines.
The purpose of the invention is realized by adopting the following technical scheme:
the invention provides a quick identification method for multi-energy complementary microgrid faults, which is improved in that the method comprises the following steps:
determining a voltage mismatching value of each line in the microgrid based on the voltage sampling value of each line in the microgrid after the fault occurs;
judging a fault line according to the voltage mismatching value of each line in the microgrid and the sum of three-phase currents;
and identifying the fault by using the voltage mismatching value of the fault line and/or the operation parameters before and after the fault.
Preferably, the determining the voltage mismatch value of each line in the microgrid based on the voltage sampling value of each line in the microgrid after the fault occurs includes:
determining the voltage mismatching value alpha of each line in the microgrid according to the following formula:
α＝2u1cos(wΔt)-u0-u2
in the above formula, u0、u1And u2The voltage sampling values at three continuous sampling moments in a fundamental wave period are respectively obtained, delta t is the sampling time interval of adjacent voltage sampling values in the fundamental wave period, and omega is the frequency of the micro-grid system.
Further, u is determined by the following formula0、u1And u2：
In the above formula, A is a voltage amplitude; t is the sampling time.
Preferably, the determining a faulty line according to the voltage mismatch value of each line in the microgrid and the sum of three-phase currents includes:
if the voltage of the line in the micro-grid is not matched and the sum of the three-phase current values meets the constraint condition, the line is a fault line; otherwise, the line is not in fault;
the constraint condition is α more than or equal to αpre-fault,95％And i isd≥id,pre-fault,95％；
Wherein α is the voltage mismatch value of the line to be tested in the microgrid idIs the sum i of three-phase currents of a tested circuit in a micro-gridd＝|ia|+|ib|+|ic|，|ia|、|ib|、|icI is A, B, C three-phase current sampling value of the measured line in the micro-grid, αpre-fault,95％For line voltage mismatch value threshold, id,pre-fault,95％Is the threshold value of the sum of three-phase currents of the line.
Further, the line voltage mismatch threshold α is determined as followspre-fault,95％：
In the above formula, the first and second carbon atoms are,
for a degree of freedom m in a chi-square distribution chart1-1 chi-square distribution value, m, corresponding to a chi-square distribution probability of 95%1N is the total number of all voltage samples in a fundamental period, sigma1 2For m calculated based on all voltage samples within one fundamental period1Estimating variance of voltage mismatching values of the tested lines in the micro-grids;
further, a sum threshold value i of three-phase currents of the line is determined according to the following formulad,pre-fault,95％：
In the above formula, the first and second carbon atoms are,
for a degree of freedom m in a chi-square distribution chart2-1 chi-square distribution value, m, corresponding to a chi-square distribution probability of 95%2The total number of sampling values, sigma, of the sum of all three-phase currents in a fundamental period2 2For m calculated based on all current sample values within one fundamental period2And the estimated variance of the sum of the three-phase currents of the tested circuit in each micro-grid.
Preferably, the fault identification by using the voltage mismatch value of the fault line and/or the operation parameters before and after the fault occurs includes:
before and after fault occurs on fault line
Determining a fault phase of a fault line by using the effective voltage value in the fundamental wave period; and/or
Determining a fault attribute of the faulty line based on the voltage mismatch value of the faulty line; and/or
And determining the fault type of the fault line based on the d-axis amplitude components of the voltage before and after the fault occurs in the fault line.
And taking the fault phase, the fault attribute and the fault type of the tested line of the microgrid as a fault identification result of the tested line of the microgrid.
Further, before and after fault occurs on the basis of fault line
Determining a fault phase of a fault line by using the effective voltage value in the fundamental wave period; and/or, comprising:
if the ith phase circuit of the fault line is in fault
Effective value of voltage V in cyclerms,pu,afterfaultSatisfy the requirement of
The ith phase circuit of the fault line is a fault phase, otherwise, the ith phase circuit of the fault line is not the fault phase;
wherein, Vrms,pu,prefaultBefore fault occurs to fault line
The effective values of the voltages in the cycle, i ∈ (a, B, C), A, B, C are the three phases of the fault line.
Further, the fault attribute of the fault line is determined based on the voltage mismatch value of the fault line; and/or, comprising:
if the voltage mismatch values α of the faulty lines are all greater than the line voltage mismatch threshold αpre-fault,95％And if not, the fault attribute of the fault line is a transient fault.
Further, the determining the fault type of the fault line based on the d-axis amplitude component of the voltage before and after the fault occurs in the fault line includes:
if the fault line has a fault, the d-axis amplitude component U of the voltage is generateddSatisfy the requirement of
The fault type of the fault line is a two-phase interphase short circuit fault; if the fault line has a fault, the d-axis amplitude component U of the voltage is generateddSatisfy the requirement of
The fault type of the fault line is a two-phase grounding short circuit fault;
wherein, UrefThe d-axis amplitude component of the voltage before the fault occurs for the faulty line.
Based on the same inventive concept, the invention also provides a multi-energy complementary microgrid fault rapid identification system, and the improvement is that the system comprises:
an acquisition module: the method comprises the steps of determining a voltage mismatching value of each line in the microgrid based on a voltage sampling value of each line in the microgrid after a fault occurs;
a judging module: the fault line judgment device is used for judging a fault line according to the voltage mismatching value of each line in the micro-grid and the sum of three-phase currents;
a fault identification module: the fault identification method is used for identifying faults by utilizing the voltage mismatching value of the fault line and/or the operation parameters before and after the fault.
Compared with the closest prior art, the invention has the following beneficial effects:
the technical scheme provided by the invention provides a method and a system for rapidly identifying the fault of a multi-energy complementary microgrid, and the method comprises the following steps of firstly, determining the voltage mismatching value of each line in the microgrid based on the voltage sampling value of each line in the microgrid after the fault occurs; secondly, judging a fault line according to the voltage mismatching value of each line in the microgrid and the sum of three-phase currents; and finally, identifying the fault by using the voltage mismatching value of the fault line and/or the operation parameters before and after the fault. According to the scheme, when the micro-grid system breaks down, the voltage and current data of the line are detected in real time, and the fault line in the micro-grid can be judged quickly and accurately by combining the relevant criterion, and fault identification is carried out.
The technical scheme provided by the invention can be used for carrying out specific fault identification on the fault line based on the fault lineBefore and after failure
Determining a fault phase of a fault line by using the effective voltage value in the fundamental wave period; and/or determining a fault attribute of the faulty line based on the voltage mismatch value of the faulty line; and/or determining the fault type of the fault line based on the d-axis amplitude component of the voltage before and after the fault occurs in the fault line, so that the effective action of relay protection is ensured, and the requirement of the relay protection speed of the microgrid is better met.
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Fig. 1 is a flowchart of a microgrid fault identification method according to an embodiment of the present invention;
FIG. 2 is a graph of voltage sample values in an embodiment of the present invention;
FIG. 3 is a simulation topology diagram of a multi-energy complementary microgrid system in an embodiment of the present invention;
FIG. 4 is a d-axis amplitude component plot of the pre-fault/post-fault voltage of the line under test of the microgrid in an embodiment of the present invention;
fig. 5 is a schematic structural diagram of a microgrid fault identification system according to an embodiment of the present invention.
Detailed Description
The following describes embodiments of the present invention in further detail with reference to the accompanying drawings.
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.
The embodiment of the invention provides a method for rapidly identifying faults of a multi-energy complementary microgrid, which comprises the following steps of:
s11, determining a voltage mismatching value of each line in the microgrid based on the voltage sampling value of each line in the microgrid after the fault occurs;
s12, judging a fault line according to the voltage mismatching value of each line in the microgrid and the sum of three-phase currents;
and S13, identifying the fault by using the voltage mismatching value of the fault line and/or the operation parameters before and after the fault.
Specifically, S11 may determine the voltage mismatch value α of each line in the microgrid according to the following formula:
α＝2u1cos(ωΔt)-u0-u2
in the above formula, u0、u1And u2The voltage sampling values at three continuous sampling moments of the line detection point in one fundamental wave period are respectively, as shown in fig. 2, adjacent phase angles at each continuous sampling moment can be different by 7.5 degrees, Δ t is a sampling time interval of adjacent voltage sampling values in one fundamental wave period, and ω is the frequency of the microgrid system.
Preferably, u can be determined as follows0、u1And u2：
In the above formula, ω is the microgrid system frequency; a is a voltage amplitude; t is the sampling time.
Specifically, S12 may include the following steps:
if the voltage mismatching value of the line in the microgrid and the sum of the three-phase currents meet the constraint condition, the line is a fault line; otherwise, the line is not in fault;
the constraint condition is α more than or equal to αpre-fault,95％And i isd≥id,pre-fault,95％；
Wherein α is the voltage mismatch value of the line to be tested in the microgrid idIs the sum i of three-phase currents of a tested circuit in a micro-gridd＝|ia|+|ib|+|ic|，|ia|、|ib|、|icRespectively A, B, C three-phase current sampling values of the tested circuit in the microgrid，αpre-fault,95％For line voltage mismatch value threshold, id,pre-fault,95％Is the threshold value of the sum of three-phase currents of the line.
Preferably, the obtaining of the parameters may be based on a mismatch value of the line voltage and a three-phase current sampling value, and specifically includes:
line voltage mismatch threshold α is determined as followspre-fault,95％：
In the above formula, the first and second carbon atoms are,
for a degree of freedom m in a chi-square distribution chart1-1 chi-square distribution value, m, corresponding to a chi-square distribution probability of 95%1N is the total number of all voltage samples in a fundamental period, sigma1 2For m calculated based on all voltage samples within one fundamental period1Estimating variance of voltage mismatching values of the tested lines in the micro-grids;
determining the sum threshold i of three-phase currents of the line according to the following formulad,pre-fault,95％：
In the above formula, the first and second carbon atoms are,
for a degree of freedom m in a chi-square distribution chart2-1 chi-square distribution value, m, corresponding to a chi-square distribution probability of 95%2The total number of sampling values, sigma, of the sum of all three-phase currents in a fundamental period2 2For m calculated based on all current sample values within one fundamental period2And the estimated variance of the sum of the three-phase currents of the tested circuit in each micro-grid.
In step S123, the operation parameters before and after the fault occurs in the faulty line may include:
fault lineBefore and after the road fault
The effective value of voltage in the fundamental wave period and/or the d-axis amplitude component of the voltage before and after the fault of the fault line.
Specifically, S13 may include the following steps:
s131, before and after fault occurs to the line based on fault
Determining a fault phase of a fault line by using the effective voltage value in the fundamental wave period; and/or
S132, determining the fault attribute of the fault line based on the voltage mismatching value of the fault line; and/or
And S133, determining the fault type of the fault line based on the d-axis amplitude components of the voltage before and after the fault occurs in the fault line.
The S131-S133 can only identify fault phases, fault attributes or fault types according to actual working condition requirements; or after identifying the fault phase, identifying the fault attribute and/or the fault type, and performing S131-S133 in a non-sequential order.
Preferably, S131 may include the steps of:
if the ith phase circuit of the fault line is in fault
Effective value of voltage V in cyclerms,pu,afterfaultSatisfy the requirement of
The ith phase circuit of the fault line is a fault phase, otherwise, the ith phase circuit of the fault line is not the fault phase;
wherein, Vrms,pu,prefaultBefore fault occurs to fault line
The effective values of the voltages in the cycle, i ∈ (a, B, C), A, B, C are the three phases of the fault line.
Preferably, S132 may include the steps of:
if the voltage mismatch values α of the faulty lines are all greater than the line voltage mismatch threshold αpre-fault,95％And if not, the fault attribute of the fault line is a transient fault.
Preferably, S133 may include the steps of:
if the fault line has a fault, the d-axis amplitude component U of the voltage is generateddSatisfy the requirement of
The fault type of the fault line is a two-phase interphase short circuit fault; if the fault line has a fault, the d-axis amplitude component U of the voltage is generateddSatisfy the requirement of
The fault type of the fault line is a two-phase grounding short circuit fault;
wherein, UrefFor the d-axis amplitude component of the voltage before the fault in the faulty line, UdAnd UrefThe method is characterized in that three-phase voltages after the fault of a tested circuit of the micro-grid and before the fault are obtained through a dq calculation formula, wherein the dq calculation formula is as follows:
in the above formula, ua、ub、ucSampled values of three-phase voltages, ud、uq、u0Respectively, voltage d-axis amplitude component sample values.
In the embodiment provided by the invention, the scheme can be verified in the application scene shown in fig. 3, the application scene shown in fig. 3 is a simulation topological graph of a multi-energy complementary microgrid system, a multi-energy complementary microgrid system model containing four typical distributed power supplies including a fan, a photovoltaic, an energy storage and a micro gas turbine is built based on RT-LAB/OP5600, and a fault identification algorithm verifies a simulation experiment. Three micro power supplies of stroke, light and micro combustion are designed in a simulation mode, PQ control is adopted, a storage battery is used as a support for voltage and frequency during off-grid operation, a VF control mode is adopted, and other micro-grid system parameters are shown in a table 1:
TABLE 1 microgrid System parameters
The experimental procedure was as follows:
1. a single-phase ground short circuit, a two-phase interphase short circuit, and a three-phase short circuit fault are respectively set at F2 in the application scenario shown in fig. 3, the fault type is identified by using the fault identification method provided by the present invention, and the fault identification result is shown in table 2:
TABLE 2 simulation results
2. As can be seen from table 2, the fast fault line selection can be completed by using the method for identifying the multi-energy complementary microgrid fault provided by the present invention, and further, the d-axis amplitude component of the voltage before/after the fault of the measured line of the microgrid is collected, and as can be seen from comparing (a) in fig. 4 with (b) in fig. 4, the amplitude of the voltage of the two-phase interphase short-circuit fault and the two-phase ground short-circuit fault is significantly different, so that the present invention can effectively determine the fault type of the measured line of the microgrid based on the d-axis amplitude component of the voltage before/after the fault of the measured line of the microgrid.
In conclusion, when different faults occur in the power transmission line of the micro-grid, the fault identification method provided by the invention can accurately and quickly complete fault line selection and fault type confirmation, so that reliable and quick actions of relay protection can be ensured, and the requirements of the relay protection on rapidity and accuracy are met.
Based on the same inventive concept, the invention also provides a multi-energy complementary microgrid fault rapid identification system, as shown in fig. 5, the system comprises:
an acquisition module: the method comprises the steps of determining a voltage mismatching value of each line in the microgrid based on a voltage sampling value of each line in the microgrid after a fault occurs;
a judging module: the fault line judgment device is used for judging a fault line according to the voltage mismatching value of each line in the micro-grid and the sum of three-phase currents;
a fault identification module: the fault identification method is used for identifying faults by utilizing the voltage mismatching value of the fault line and/or the operation parameters before and after the fault.
Preferably, the acquisition module is specifically configured to:
determining the voltage mismatching value alpha of each line in the microgrid according to the following formula:
α＝2u1cos(ωΔt)-u0-u2
in the above formula, u0、u1And u2The voltage sampling values of three continuous sampling moments of the line detection point in one fundamental wave period are respectively, delta t is the sampling time interval of adjacent voltage sampling values in one fundamental wave period, and omega is the frequency of the micro-grid system.
U is determined by0、u1And u2：
In the above formula, ω is the microgrid system frequency; a is a voltage amplitude; t is the sampling time.
Preferably, the determining module is specifically configured to:
if the voltage mismatching value of the line in the microgrid and the sum of the three-phase currents meet the constraint condition, the line is a fault line; otherwise, the line is not in fault;
the constraint condition is α more than or equal to αpre-fault,95％And i isd≥id,pre-fault,95％；
Wherein α is the voltage mismatch value of the line to be tested in the microgrid idIs the sum i of three-phase currents of a tested circuit in a micro-gridd＝|ia|+|ib|+|ic|，|ia|、|ib|、|icI is A, B, C three-phase current sampling value of the measured line in the micro-grid, αpre-fault,95％For line voltage mismatch value threshold, id,pre-fault,95％Is the threshold value of the sum of three-phase currents of the line.
Preferably, the judging module is further configured to:
line voltage mismatch threshold α is determined as followspre-fault,95％：
In the above formula, the first and second carbon atoms are,
for a degree of freedom m in a chi-square distribution chart1-1 chi-square distribution value, m, corresponding to a chi-square distribution probability of 95%1N is the total number of all voltage samples in a fundamental period, sigma1 2For m calculated based on all voltage samples within one fundamental period1Estimating variance of voltage mismatching values of the tested lines in the micro-grids;
determining the sum threshold i of three-phase currents of the line according to the following formulad,pre-fault,95％：
In the above formula, the first and second carbon atoms are,
for a degree of freedom m in a chi-square distribution chart2-1 chi-square distribution value, m, corresponding to a chi-square distribution probability of 95%2The total number of sampling values, sigma, of the sum of all three-phase currents in a fundamental period2 2For m calculated based on all current sample values within one fundamental period2And the estimated variance of the sum of the three-phase currents of the tested circuit in each micro-grid.
Preferably, the operation parameters before and after the fault line fault may include:
before and after fault of fault line
Effective value of voltage in fundamental wave period and/or d-axis amplitude component of voltage before and after fault of fault line
Preferably, the fault identification module includes:
a first determination unit for determining before and after fault occurrence based on the fault line
Determining a fault phase of a fault line by using the effective voltage value in the fundamental wave period; and/or
A second determination unit for determining a fault attribute of the faulty line based on the voltage mismatch value of the faulty line; and/or
And the third determination unit is used for determining the fault type of the fault line based on the d-axis amplitude components of the voltage before and after the fault occurs in the fault line.
Preferably, the fault identification module further includes:
and the result generation unit is used for taking the fault phase, the fault attribute and/or the fault type of the tested line of the microgrid as a fault identification result of the tested line of the microgrid.
Further, the first determining unit is specifically configured to:
if the ith phase circuit of the fault line is in fault
Effective value of voltage V in cyclerms,pu,afterfaultSatisfy the requirement of
The ith phase circuit of the fault line is a fault phase, otherwise, the ith phase circuit of the fault line is not the fault phase;
wherein, Vrms,pu,prefaultBefore fault occurs to fault line
The effective values of the voltages in the cycle, i ∈ (a, B, C), A, B, C are the three phases of the fault line.
Further, the second determining unit is specifically configured to:
if the voltage mismatch values α of the faulty lines are all greater than the line voltage mismatch threshold αpre-fault,95％And if not, the fault attribute of the fault line is a transient fault.
Further, the third determining unit is specifically configured to:
if the fault line has a fault, the d-axis amplitude component U of the voltage is generateddSatisfy the requirement of
The fault type of the fault line is a two-phase interphase short circuit fault; if the fault line has a fault, the d-axis amplitude component U of the voltage is generateddSatisfy the requirement of
The fault type of the fault line is a two-phase grounding short circuit fault;
wherein, UrefFor the d-axis amplitude component of the voltage before the fault in the faulty line, UdAnd UrefThe method is characterized in that three-phase voltages after the fault of a tested circuit of the micro-grid and before the fault are obtained through a dq calculation formula, wherein the dq calculation formula is as follows:
in the above formula, ua、ub、ucSampled values of three-phase voltages, ud、uq、u0Respectively, voltage d-axis amplitude component sample values.
As will be appreciated by one skilled in the art, embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.
The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the application. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solutions of the present invention and not for limiting the same, and although the present invention is described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: modifications and equivalents may be made to the embodiments of the invention without departing from the spirit and scope of the invention, which is to be covered by the claims.
Claims (10)
1. A multi-energy complementary microgrid fault rapid identification method is characterized by comprising the following steps:
determining a voltage mismatching value of each line in the microgrid based on the voltage sampling value of each line in the microgrid after the fault occurs;
judging a fault line according to the voltage mismatching value of each line in the microgrid and the sum of three-phase currents;
and identifying the fault by using the voltage mismatching value of the fault line and/or the operation parameters before and after the fault.
2. The method of claim 1, wherein determining a voltage mismatch value for each line in the microgrid based on voltage sample values for each line in the microgrid after the fault occurs comprises:
determining the voltage mismatching value alpha of each line in the microgrid according to the following formula:
α＝2u1cos(ωΔt)-u0-u2
in the above formula, u0、u1And u2The voltage sampling values of three continuous sampling moments of the line detection point in one fundamental wave period are respectively, delta t is the sampling time interval of adjacent voltage sampling values in one fundamental wave period, and omega is the frequency of the micro-grid system.
3. The method of claim 2, wherein u is determined according to the following equation0、u1And u2：
In the above formula, A is a voltage amplitude; t is the sampling time.
4. The method of claim 1, wherein the determining the faulty line according to the voltage mismatch value of each line in the microgrid and the sum of three-phase currents comprises:
if the voltage mismatching value of the line in the microgrid and the sum of the three-phase currents meet the constraint condition, the line is a fault line; otherwise, the line is not in fault;
the constraint condition is α more than or equal to αpre-fault,95％And i isd≥id,pre-fault,95％；
Wherein α is the voltage mismatch value of the line to be tested in the microgrid idIs the sum i of three-phase currents of a tested circuit in a micro-gridd＝|ia|+|ib|+|ic|，|ia|、|ib|、|icI is A, B, C three-phase current sampling value of the measured line in the micro-grid, αpre-fault,95％For line voltage mismatch value threshold, id,pre-fault,95％Is the threshold value of the sum of three-phase currents of the line.
5. The method of claim 4, wherein the line voltage mismatch threshold α is determined as followspre-fault,95％：
In the above formula, the first and second carbon atoms are,
for a degree of freedom m in a chi-square distribution chart1-1 chi-square distribution value, m, corresponding to a chi-square distribution probability of 95%1N is the total number of all voltage samples in a fundamental period, sigma1 2For m calculated based on all voltage samples within one fundamental period1Estimating variance of voltage mismatching values of the tested lines in the micro-grids;
determining the sum threshold i of three-phase currents of the line according to the following formulad,pre-fault,95％：
In the above formula, the first and second carbon atoms are,
for a degree of freedom m in a chi-square distribution chart2-1 chi-square distribution value, m, corresponding to a chi-square distribution probability of 95%2The total number of sampling values, sigma, of the sum of all three-phase currents in a fundamental period2 2For m calculated based on all current sample values within one fundamental period2And the estimated variance of the sum of the three-phase currents of the tested circuit in each micro-grid.
6. The method of claim 1, wherein the operating parameters before and after the fault line fault comprise:
before and after fault of fault line
The effective value of voltage in a fundamental wave period and/or the d-axis amplitude component of voltage before and after a fault occurs in a fault line;
the fault identification is carried out by utilizing the voltage mismatching value of the fault line and/or the operation parameters before and after the fault, and comprises the following steps:
before and after fault occurs on fault line
Determining a fault phase of a fault line by using the effective voltage value in the fundamental wave period; and/or
Determining a fault attribute of the faulty line based on the voltage mismatch value of the faulty line; and/or
And determining the fault type of the fault line based on the d-axis amplitude components of the voltage before and after the fault occurs in the fault line.
7. The method of claim 6, wherein the fault-based line is pre-faulted and post-faulted
The method for determining the fault phase of the fault line by the effective voltage value in the fundamental wave period comprises the following steps:
if the ith phase circuit of the fault line has fault
Effective value of voltage V in cyclerms,pu,afterfaultSatisfy the requirement of
The ith phase circuit of the fault line is a fault phase, otherwise, the ith phase circuit of the fault line is not the fault phase;
wherein, Vrms,pu,prefaultBefore the i-th phase circuit of the fault line fails
The effective values of the voltages in the cycle, i ∈ (a, B, C), A, B, C are the three phases of the fault line.
8. The method of claim 6, wherein determining the fault attribute of the faulty line based on the voltage mismatch value for the faulty line comprises:
if the voltage mismatch values α of the faulty lines are all greater than the line voltage mismatch threshold αpre-fault,95％And if not, the fault attribute of the fault line is a transient fault.
9. The method of claim 6, wherein determining the fault type of the faulty line based on the d-axis magnitude components of the voltage before and after the faulty line fault comprises:
if the fault line has a fault, the d-axis amplitude component U of the voltage is generateddSatisfy the requirement of
The fault type of the fault line is a two-phase interphase short circuit fault; if the fault line has fault, the power supply is turned onD-axis amplitude component UdSatisfy the requirement of
The fault type of the fault line is a two-phase grounding short circuit fault;
wherein, UrefThe d-axis amplitude component of the voltage before the fault occurs for the faulty line.
10. A multi-energy complementary microgrid fault rapid identification system is characterized in that the system comprises:
an acquisition module: determining a voltage mismatching value of each line in the microgrid based on the voltage sampling value of each line in the microgrid after the fault occurs;
a judging module: the fault line judgment device is used for judging a fault line according to the voltage mismatching value of each line in the microgrid and the sum of three-phase current values;
a fault identification module: the fault identification method is used for identifying faults by utilizing the voltage mismatching value of the fault line and/or the operation parameters before and after the fault.
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| CN115035692A (en) * | 2022-05-23 | 2022-09-09 | 国家电网有限公司技术学院分公司 | Alarm method, system, medium and equipment for automatically judging faults of each phase of power transmission line |
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| CN112598141A (en) * | 2020-11-09 | 2021-04-02 | 国网上海能源互联网研究院有限公司 | Operation and maintenance method and system for regional photovoltaic power station |
| CN115035692A (en) * | 2022-05-23 | 2022-09-09 | 国家电网有限公司技术学院分公司 | Alarm method, system, medium and equipment for automatically judging faults of each phase of power transmission line |
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