CN110611304A - Power distribution network low-voltage risk online early warning method and system - Google Patents
Power distribution network low-voltage risk online early warning method and system Download PDFInfo
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- CN110611304A CN110611304A CN201810613713.3A CN201810613713A CN110611304A CN 110611304 A CN110611304 A CN 110611304A CN 201810613713 A CN201810613713 A CN 201810613713A CN 110611304 A CN110611304 A CN 110611304A
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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
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/04—Circuit arrangements for ac mains or ac distribution networks for connecting networks of the same frequency but supplied from different sources
- H02J3/06—Controlling transfer of power between connected networks; Controlling sharing of load between connected networks
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y04—INFORMATION OR COMMUNICATION TECHNOLOGIES HAVING AN IMPACT ON OTHER TECHNOLOGY AREAS
- Y04S—SYSTEMS INTEGRATING TECHNOLOGIES RELATED TO POWER NETWORK OPERATION, COMMUNICATION OR INFORMATION TECHNOLOGIES FOR IMPROVING THE ELECTRICAL POWER GENERATION, TRANSMISSION, DISTRIBUTION, MANAGEMENT OR USAGE, i.e. SMART GRIDS
- Y04S10/00—Systems supporting electrical power generation, transmission or distribution
- Y04S10/50—Systems or methods supporting the power network operation or management, involving a certain degree of interaction with the load-side end user applications
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Abstract
The invention provides a power distribution network low-voltage risk online early warning method and a system, comprising the following steps: calculating load moments of preset lines in the power distribution network according to the real-time monitoring data and the load prediction data of the power distribution network; and calculating the voltage of a preset load point on a preset line according to the load moment calculation result, and judging whether the power distribution network has a low-voltage out-of-limit risk in a preset future time period according to a preset low-voltage out-of-limit early warning judgment rule. The method and the system provide decision basis for reasonably improving the power supply quality of the power distribution network, can accurately early warn the low voltage risk of the power distribution network, and have the advantages of good practicability, simple calculation and easy operation.
Description
Technical Field
The invention belongs to the technical field of risk analysis and control of a power distribution network, and particularly relates to a low-voltage risk online early warning method and system for the power distribution network.
Background
In a power distribution network, too long lines, heavier loads, insufficient reactive compensation, unreasonable load distribution, unbalanced distribution and transformation three phases, small wire sections, serious deviation of distribution and transformation from load centers, overlarge power supply radius of distribution and transformation and the like all cause low voltage and increased current, and line overload is possible to occur.
In the actual operation of distribution network, when distribution lines load increase or the overload operation, the line voltage drop increases gradually, surpasss normal allowable range, if the reactive compensation of circuit is not enough, the line load lasts to increase, leads to the voltage drop to last the increase for a long time, then can lead to the terminal low voltage risk of taking place of circuit. The distribution network low voltage appears, will greatly influence daily production and life, and the emergence of circuit low voltage will lead to following consequence: (1) the line loss is increased, and the efficiency is reduced; (2) the electric appliances are difficult to start and have overhigh temperature rise; (3) the brightness of the incandescent lamp is reduced, so that the fluorescent lamp cannot be started; (4) affecting the image quality of the screen electrical appliance; (5) affecting the normal heating of the electric heating appliances.
At present, measures such as distribution transformation capacity increase, reactive compensation, heavy load line shunt and the like are generally adopted for treating the low voltage phenomenon of the power distribution network, but the measures have certain hysteresis, namely the low voltage phenomenon is often treated.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention provides a power distribution network low-voltage risk online early warning method and system, which are used for early warning the low-voltage drop amplitude of a power distribution network.
The adopted solution for realizing the purpose is as follows:
the improvement of the online early warning method for low voltage risk of the power distribution network is that,
calculating load moments of preset lines in the power distribution network according to the real-time monitoring data and the load prediction data of the power distribution network;
and calculating the voltage of a preset load point on the preset line according to the load moment calculation result, and judging whether the power distribution network has a low-voltage out-of-limit risk in a preset future time period according to a preset low-voltage out-of-limit early warning judgment rule.
According to the first preferred technical scheme provided by the invention, the improvement is that the load moment of a preset line in the power distribution network is calculated according to the real-time monitoring data and the load prediction data of the power distribution network as follows:
M＝∑P×L (1)
the method comprises the steps that M is a load moment of a line on a time node, P represents load prediction data of a preset load point of the time node on the line, L represents an electric distance between the load point on the line and a power supply, wherein the electric distance is obtained from real-time monitoring data of a power distribution network, and Σ represents summation of the preset load point of the time node on the line.
The second preferred technical solution provided by the present invention is improved in that the calculating, according to the load moment calculation result, the voltage of a preset load point on the line is calculated, and whether there is a low voltage out-of-limit risk in the distribution network in a preset future time period is determined according to a preset low voltage out-of-limit warning determination rule, and the method includes:
sequentially calculating voltage values of preset load points on time nodes of the line in a preset future time period according to the sequence of the load moments from large to small, and judging that the predicted low voltage threshold crossing exists at the time nodes corresponding to the load moments until the predicted low voltage threshold crossing does not exist at the time nodes corresponding to the load moments when the voltage of the load points is lower than a preset voltage lower limit value;
judging whether historical low-voltage out-of-limit exists at the corresponding moment of each time node in the preset future time period of the preset load point according to historical voltage data of the corresponding moment of each time node in the preset future time period of the preset load point of the power distribution network;
when the predicted low voltage out-of-limit and the historical low voltage out-of-limit do not exist in the time node, giving an early warning result that the time node is normal; otherwise, giving out an early warning result that the low voltage threshold crossing risk exists.
The third preferred technical solution provided by the present invention is improved in that, according to the order of the load moment from large to small, the voltage values of the preset load points on the time nodes of the preset line in the preset future time period are sequentially calculated, and when the voltage of the load point is lower than the preset lower voltage limit value, it is determined that the predicted lower voltage limit of the line at the time node corresponding to the load moment exists, until the load moment does not have the preset lower voltage limit, the method includes:
sequentially selecting preset time nodes of the line in a preset future time period according to the sequence of the load moments from large to small, carrying out load flow calculation to obtain a voltage value of a preset load point, and judging as follows:
if the voltage value of a load point is lower than a preset voltage lower limit value, judging that the predicted low voltage out-of-limit exists at a time node corresponding to the load moment on the line;
otherwise, setting the load moment as a standard load moment of the line, judging that no low-voltage out-of-limit exists at a time node when the line load moment is smaller than the standard load moment, and stopping load flow calculation.
The fourth preferred technical solution provided by the present invention is improved in that, in combination with historical voltage data of a preset load point of the power distribution network at a time corresponding to each time node in a preset future time period, determining whether there is a historical low voltage out-of-limit at the time corresponding to each time node in the preset future time period by the preset load point includes:
acquiring historical voltage data of each load point at the same time in one day corresponding to each time node in a preset time period, and judging whether the historical voltage data is lower than a voltage lower limit value: if so, judging that the historical low voltage threshold of the time node exists, otherwise, judging that the historical low voltage threshold of the time node does not exist.
The fifth preferred technical solution provided by the present invention is improved in that after the warning result is given, the method further comprises:
if the early warning result is normal, ending the early warning process and waiting for the next early warning start;
otherwise, issuing early warning information and tracking an early warning result;
the early warning information includes time nodes, lines, load nodes and voltage amplitudes for which low voltage violations are predicted.
In a sixth preferred technical solution provided by the present invention, the improvement is that the tracking and early warning result includes:
when the topology of the power distribution network changes, low-voltage risk early warning is carried out again according to the latest load prediction data, if the early warning result is normal, early warning information is cancelled, the early warning process is ended, and the next early warning is started; otherwise, issuing early warning information and tracking an early warning result;
when the topology of the power distribution network does not change, if the load changes, starting an early warning process according to the latest load prediction, and if the early warning result is normal, canceling early warning information, ending the early warning process and waiting for the next start; otherwise, issuing early warning information and tracking an early warning result;
when the topology and the load of the power distribution network are not changed, waiting until the moment of low voltage out-of-limit in early warning is reached, and if the low voltage out-of-limit does not occur, canceling early warning information; otherwise, the moment when the low voltage exceeds the limit and the voltage amplitude are obtained, and the early warning information is cancelled.
The utility model provides a distribution network low voltage risk online early warning system which improves and lies in, includes: the system comprises a load moment calculation module and a risk prediction module;
the load moment calculation module is used for calculating the load moment of a preset line in the power distribution network according to the real-time monitoring data and the load prediction data of the power distribution network;
the risk prediction module is used for calculating the voltage of a preset load point on the preset line according to the load moment calculation result, and judging whether the power distribution network has a low-voltage out-of-limit risk in a future time period according to a preset low-voltage out-of-limit early warning judgment rule.
In a seventh preferred aspect of the present invention, the improvement wherein the load moment calculation module includes: the load moment calculating unit is used for calculating the load moment of the load;
the data acquisition subunit is used for acquiring load prediction data of each time node in a preset time period and acquiring the electrical distance from a preset load point in the power distribution network to a power supply from the real-time monitoring data of the power distribution network;
the load moment calculation subunit is configured to calculate load moments of lines preset at each time node in the power distribution network according to the following formula:
M＝∑P×L (1)
the method comprises the steps that M is a load moment of a line on a time node, P represents load prediction data of a preset load point of the time node on the line, L represents an electric distance between the load point on the line and a power supply, wherein the electric distance is obtained from real-time monitoring data of a power distribution network, and Σ represents summation of the preset load point of the time node on the line.
In an eighth preferred aspect of the present invention, the improvement wherein the risk prediction module comprises: the system comprises a future judgment subunit, a history judgment subunit and an early warning subunit;
the future judging subunit is used for sequentially calculating voltage values of preset load points on time nodes of the line in a preset future time period according to the sequence of the load moments from large to small, and judging that the predicted low voltage out-of-limit exists in the time nodes corresponding to the load moments of the line when the voltage of the load points is lower than a preset voltage lower limit value until the predicted low voltage out-of-limit does not exist in the time nodes corresponding to the load moments;
the history judging subunit is used for judging whether history low-voltage out-of-limit exists at the corresponding moment of each time node in the preset future time period of the preset load point according to the history voltage data of the corresponding moment of each time node in the preset future time period of the preset load point of the power distribution network;
the early warning subunit is used for giving an early warning result as normal when the predicted low voltage out-of-limit and the historical low voltage out-of-limit do not exist in the time node; otherwise, giving out an early warning result that the low voltage threshold crossing risk exists.
The improvement of the ninth preferred technical proposal provided by the invention is that the device also comprises a tracking module;
the tracking module is used for ending the early warning process and waiting for the next early warning start if the early warning result is normal;
otherwise, issuing early warning information and tracking an early warning result;
the early warning information includes time nodes, lines, load nodes and voltage amplitudes for which low voltage violations are predicted.
In a tenth preferred aspect of the present invention, the improvement wherein the tracking module includes: a topology change subunit, a load change subunit and an invariant subunit;
the topology change subunit is used for carrying out low-voltage risk early warning again according to the latest load prediction data when the topology of the power distribution network changes, and if the early warning result is normal, canceling the early warning information and waiting for the next early warning start; otherwise, issuing early warning information and tracking an early warning result;
the load change subunit is used for predicting and starting an early warning process according to the latest load if the load changes when the topology of the power distribution network does not change, and canceling the early warning information, ending the early warning process and waiting for the next start if the early warning result is normal; otherwise, issuing early warning information and tracking an early warning result;
the invariant subunit is used for waiting until the early warning is carried out at the moment that the low voltage is out of limit when the topology and the load of the power distribution network are not changed, and canceling the early warning information if the low voltage is not out of limit; otherwise, the moment when the low voltage exceeds the limit and the voltage amplitude are obtained, and the early warning information is cancelled.
Compared with the closest prior art, the invention has the following beneficial effects:
the invention provides a power distribution network low-voltage risk online early warning method and a power distribution network low-voltage risk online early warning system, which aim to calculate a load moment according to power grid real-time monitoring data and load prediction data, calculate and evaluate a preset node voltage index on a preset line according to a calculation result of the load moment, judge whether a power distribution network has a voltage out-of-limit risk in a preset future time period according to a preset low-voltage out-of-limit early warning judgment rule, provide a decision basis for reasonably improving power supply quality of the power distribution network, accurately early warn the power distribution network low-voltage risk, and have the advantages of good practicability, simplicity in calculation and easiness in operation.
Drawings
Fig. 1 is a schematic flow chart of a low-voltage risk online early warning method for a power distribution network provided by the invention.
Detailed Description
The following describes embodiments of the present invention in further detail with reference to the accompanying drawings.
The schematic flow diagram of the low-voltage risk monitoring and early warning method for the power distribution network provided by the invention is shown in fig. 1, and comprises the following steps:
calculating load moments of preset lines in the power distribution network according to the real-time monitoring data and the load prediction data of the power distribution network;
and calculating the voltage of a preset load point on a preset line according to the load moment calculation result, and judging whether the power distribution network has a low-voltage out-of-limit risk in a preset future time period according to a preset low-voltage out-of-limit early warning judgment rule.
Specifically, the online early warning method for the low voltage risk of the power distribution network comprises the following specific steps:
step 1: acquiring load prediction data of each time node in a future preset time period, and calculating the load moment M of a preset line at the time node according to the following formula:
M＝∑P×L (1)
the power of the load point is P, the electrical distance from the load point to the power point is L, and sigma represents summing the preset load points of the same time node on the same line.
Step 2: and sequencing the load moments in the route prediction time period from large to small.
And step 3: and selecting a time node corresponding to the maximum load moment, performing load flow calculation, and storing the voltage value of each load point.
And 4, step 4: and judging whether the voltage of each load point is lower than a preset voltage lower limit value or not under the time node corresponding to the maximum load moment.
And 5: if the voltage of the load point is lower than the lower voltage limit value, the predicted low voltage out-of-limit exists at the time node t' corresponding to the maximum load moment of the line, the corresponding load moment and the time node, the voltage amplitude and the load node of the voltage out-of-limit at the time are recorded, and the step 6 is carried out;
if the voltage is in the normal range, recording the corresponding load moment, taking the load moment at the moment as the standard load moment of the line, judging that the predicted low voltage out-of-limit does not exist in the time node when the line load moment is smaller than the standard load moment, and executing the step 8.
Step 6: and selecting a time node corresponding to the next maximum load moment to perform load flow calculation.
And 7: if the voltage of the load point is lower than the lower limit value of the voltage, the predicted lower voltage out-of-limit exists at the time point t' corresponding to the load moment on the line, the corresponding load moment and voltage out-of-limit time node, the voltage amplitude and the load node at the time point are recorded, and the step 6 is returned.
If the voltage is in the normal range, the moment of load is recorded, the moment of load at that moment is taken as the standard moment of load of the line, and step 8 is executed.
And 8: and (4) judging whether the power grid has voltage out-of-limit risks or not according to the low-voltage out-of-limit early warning judgment rule by combining the voltage conditions of each load point of each time node in the prediction time period of historical statistics, and giving an early warning result. And the historical voltage data in the historical statistics is the voltage data of the load points of each time node at the same time in one day.
Judging whether the historical voltage data is lower than a voltage lower limit value: if so, judging that the historical low voltage threshold crossing exists in the corresponding time node, otherwise, judging that the historical low voltage threshold crossing does not exist in the corresponding time node;
when the predicted low voltage out-of-limit and the historical low voltage out-of-limit do not exist in the time node, the early warning result is normal;
when any one of the predicted low-voltage out-of-limit and the historical low-voltage out-of-limit exists in the time node, the early warning result indicates that the low-voltage out-of-limit risk exists.
The low voltage out-of-limit warning and judgment rules are summarized in table 1 below.
TABLE 1 Low Voltage out-of-limit Warning and judgment rules
And step 9: one line calculation ends.
Step 10: and (5) repeating the steps 1 to 9 on the preset line, and after the calculation is finished, storing and statistically analyzing the calculation result. And issuing early warning information after all lines are calculated.
Step 11: if no early warning exists, the early warning process is ended, and the next early warning is started.
Step 12: and if the early warning exists, tracking the early warning result.
The early warning result of distribution network low voltage risk is tracked, needs to track to the network topology situation of change, and specific content includes:
the topology changes, the load moment correspondingly changes, and the judgment is carried out according to two conditions:
(1) when the topology changes, the low voltage risk early warning step is carried out again according to the latest load prediction result, if the result is that no low voltage exists, early warning information is cancelled, the current voltage amplitude value in normal operation is recorded, the early warning process is ended, and the next start is waited; and if the low voltage still exists, still issuing early warning information and tracking the low voltage risk.
(2) And when the topology is not changed, if the load is changed, starting an early warning process according to the latest load prediction, if the result is that no low voltage exists, canceling the early warning information, recording the current voltage amplitude value in normal operation, ending the early warning process, and waiting for the next start. If there is still low voltage, then low voltage risk tracking is performed. If the load is not changed, waiting until the time of early warning of low voltage is reached, and if the low voltage is not generated, recording the current voltage amplitude of normal operation and canceling early warning information; if the low voltage occurs, recording the occurrence of low voltage out-of-limit at the moment, recording the voltage amplitude, and canceling the early warning information.
Based on the same invention concept, the invention also provides a power distribution network low-voltage risk online early warning system, and as the principle of solving the technical problems by the devices is similar to the power distribution network low-voltage risk online early warning method, repeated parts are not repeated.
The system comprises a load moment calculation module and a risk prediction module;
the load moment calculation module is used for calculating the load moment of a preset line in the power distribution network according to the real-time monitoring data and the load prediction data of the power distribution network;
the risk prediction module is used for calculating the voltage of a preset load point on a preset line according to the load moment calculation result, and judging whether the power distribution network has a low-voltage out-of-limit risk in a future time period according to a preset low-voltage out-of-limit early warning judgment rule.
Wherein, load moment calculation module includes: the load moment calculating unit is used for calculating the load moment of the load;
the data acquisition subunit is used for acquiring load prediction data of each time node in a preset time period and acquiring the electrical distance from a preset load point in the power distribution network to a power supply from the real-time monitoring data of the power distribution network;
the load moment calculation subunit is used for calculating the load moment of a line preset on each time node in the power distribution network according to the following formula:
M＝∑P×L (1)
wherein M is the load moment of a line on a time node, P represents the load prediction data of a preset load point of the time node on the line, L represents the electrical distance from the load point on the line to a power supply, and Σ represents the summation of the preset load points of the time nodes on the same line.
Wherein the risk prediction module comprises: the system comprises a future judgment subunit, a history judgment subunit and an early warning subunit;
the future judgment subunit is used for sequentially calculating voltage values of preset load points on time nodes of a preset line in a preset future time period according to the sequence of the load moments from large to small, and judging that the predicted low voltage threshold crossing exists in the time nodes corresponding to the load moments of the line when the voltage of the load points is lower than a preset voltage lower limit value until the predicted low voltage threshold crossing does not exist in the time nodes corresponding to the load moments;
the history judgment subunit is used for judging whether history low-voltage out-of-limit exists at the corresponding moment of each time node in the preset future time period of the preset load point according to the history voltage data of the corresponding moment of each time node in the preset future time period of the preset load point of the power distribution network;
the early warning subunit is used for giving an early warning result as normal when the predicted low voltage out-of-limit and the historical low voltage out-of-limit do not exist in the time node; otherwise, giving out an early warning result that the low voltage threshold crossing risk exists.
The system also includes a tracking module;
the tracking module is used for finishing the early warning process and waiting for the next early warning starting if the early warning result is normal;
otherwise, issuing early warning information and tracking an early warning result;
the early warning information includes time nodes, lines, load nodes and voltage amplitudes for which a low voltage out-of-limit is predicted to exist.
Wherein, the tracking module includes: a topology change subunit, a load change subunit and an invariant subunit;
the topology change subunit is used for carrying out low-voltage risk early warning again according to the latest load prediction data when the topology of the power distribution network changes, canceling early warning information if the early warning result is normal, ending the early warning process and waiting for the next early warning start; otherwise, issuing early warning information and tracking an early warning result;
the load change subunit is used for predicting and starting an early warning process according to the latest load if the load changes when the topology of the power distribution network does not change, canceling the early warning information if the early warning result is normal, ending the early warning process and waiting for the next start; otherwise, issuing early warning information and tracking an early warning result;
the invariant subunit is used for waiting when the topology and the load of the power distribution network are not changed until the early warning moment that the low voltage exceeds the limit, and canceling the early warning information if the low voltage does not exceed the limit; otherwise, the moment when the low voltage exceeds the limit and the voltage amplitude are obtained, and the early warning information is cancelled.
It should be noted that the above-mentioned embodiments are only for illustrating the technical solutions of the present application and not for limiting the scope of protection thereof, and although the present application is described in detail with reference to the above-mentioned embodiments, those skilled in the art should understand that after reading the present application, they can make various changes, modifications or equivalents to the specific embodiments of the application, but these changes, modifications or equivalents are all within the scope of protection of the claims to be filed.
Claims (12)
1. A power distribution network low-voltage risk online early warning method is characterized by comprising the following steps:
calculating load moments of preset lines in the power distribution network according to the real-time monitoring data and the load prediction data of the power distribution network;
and calculating the voltage of a preset load point on the preset line according to the load moment calculation result, and judging whether the power distribution network has a low-voltage out-of-limit risk in a preset future time period according to a preset low-voltage out-of-limit early warning judgment rule.
2. The method of claim 1, wherein the load moment of the preset line in the distribution network is calculated according to the real-time monitoring data and the load prediction data of the distribution network as follows:
M＝∑P×L (1)
the method comprises the steps that M is a load moment of a line on a time node, P represents load prediction data of a preset load point of the time node on the line, L represents an electric distance between the load point on the line and a power supply, wherein the electric distance is obtained from real-time monitoring data of a power distribution network, and Σ represents summation of the preset load point of the time node on the line.
3. The method of claim 1, wherein the step of calculating the preset voltage of the preset load point on the line according to the load moment calculation result and judging whether the power distribution network has a low voltage out-of-limit risk in a preset future time period according to a preset low voltage out-of-limit early warning judgment rule comprises the steps of:
sequentially calculating voltage values of preset load points on time nodes of the line in a preset future time period according to the sequence of the load moments from large to small, and judging that the predicted low voltage threshold crossing exists at the time nodes corresponding to the load moments until the predicted low voltage threshold crossing does not exist at the time nodes corresponding to the load moments when the voltage of the load points is lower than a preset voltage lower limit value;
judging whether historical low-voltage out-of-limit exists at the corresponding moment of each time node in the preset future time period of the preset load point according to historical voltage data of the corresponding moment of each time node in the preset future time period of the preset load point of the power distribution network;
when the predicted low voltage out-of-limit and the historical low voltage out-of-limit do not exist in the time node, giving an early warning result that the time node is normal; otherwise, giving out an early warning result that the low voltage threshold crossing risk exists.
4. The method according to claim 3, wherein the step of sequentially calculating preset voltage values of preset load points on time nodes of the line in a preset future time period according to the sequence from large load moment to small load moment, and when the voltage of the load point is lower than a preset lower voltage limit value, judging that the predicted lower voltage limit of the line at the time node corresponding to the load moment exists until the load moment does not have the preset lower voltage limit, comprises the steps of:
sequentially selecting preset time nodes of the line in a preset future time period according to the sequence of the load moments from large to small, carrying out load flow calculation to obtain a voltage value of a preset load point, and judging as follows:
if the voltage value of a load point is lower than a preset voltage lower limit value, judging that the predicted low voltage out-of-limit exists at a time node corresponding to the load moment on the line;
otherwise, setting the load moment as a standard load moment of the line, judging that no low-voltage out-of-limit exists at a time node when the line load moment is smaller than the standard load moment, and stopping load flow calculation.
5. The method of claim 3, wherein the determining whether there is a historical low voltage threshold crossing at the time corresponding to each time node within the preset future time period for the preset load point in combination with historical voltage data at the time corresponding to each time node within the preset future time period for the preset load point of the power distribution network comprises:
acquiring historical voltage data of each load point at the same time in one day corresponding to each time node in a preset time period, and judging whether the historical voltage data is lower than a voltage lower limit value: if so, judging that the historical low voltage threshold of the time node exists, otherwise, judging that the historical low voltage threshold of the time node does not exist.
6. The method of claim 3, wherein after the warning is given, further comprising:
if the early warning result is normal, ending the early warning process and waiting for the next early warning start;
otherwise, issuing early warning information and tracking an early warning result;
the early warning information includes time nodes, lines, load nodes and voltage amplitudes for which low voltage violations are predicted.
7. The method of claim 6, wherein the tracking pre-warning result comprises:
when the topology of the power distribution network changes, low-voltage risk early warning is carried out again according to the latest load prediction data, if the early warning result is normal, early warning information is cancelled, the early warning process is ended, and the next early warning is started; otherwise, issuing early warning information and tracking an early warning result;
when the topology of the power distribution network does not change, if the load changes, starting an early warning process according to the latest load prediction, and if the early warning result is normal, canceling early warning information, ending the early warning process and waiting for the next start; otherwise, issuing early warning information and tracking an early warning result;
when the topology and the load of the power distribution network are not changed, waiting until the moment of low voltage out-of-limit in early warning is reached, and if the low voltage out-of-limit does not occur, canceling early warning information; otherwise, the moment when the low voltage exceeds the limit and the voltage amplitude are obtained, and the early warning information is cancelled.
8. The utility model provides a distribution network low voltage risk online early warning system which characterized in that includes: the system comprises a load moment calculation module and a risk prediction module;
the load moment calculation module is used for calculating the load moment of a preset line in the power distribution network according to the real-time monitoring data and the load prediction data of the power distribution network;
the risk prediction module is used for calculating the voltage of a preset load point on the preset line according to the load moment calculation result, and judging whether the power distribution network has a low-voltage out-of-limit risk in a future time period according to a preset low-voltage out-of-limit early warning judgment rule.
9. The system of claim 8, wherein the loading moment calculation module comprises: the load moment calculating unit is used for calculating the load moment of the load;
the data acquisition subunit is used for acquiring load prediction data of each time node in a preset time period and acquiring the electrical distance from a preset load point in the power distribution network to a power supply from the real-time monitoring data of the power distribution network;
the load moment calculation subunit is configured to calculate load moments of lines preset at each time node in the power distribution network according to the following formula:
M＝∑P×L (1)
the method comprises the steps that M is a load moment of a line on a time node, P represents load prediction data of a preset load point of the time node on the line, L represents an electric distance between the load point on the line and a power supply, wherein the electric distance is obtained from real-time monitoring data of a power distribution network, and Σ represents summation of the preset load point of the time node on the line.
10. The system of claim 8, wherein the risk prediction module comprises: the system comprises a future judgment subunit, a history judgment subunit and an early warning subunit;
the future judging subunit is used for sequentially calculating voltage values of preset load points on time nodes of the line in a preset future time period according to the sequence of the load moments from large to small, and judging that the predicted low voltage out-of-limit exists in the time nodes corresponding to the load moments of the line when the voltage of the load points is lower than a preset voltage lower limit value until the predicted low voltage out-of-limit does not exist in the time nodes corresponding to the load moments;
the history judging subunit is used for judging whether history low-voltage out-of-limit exists at the corresponding moment of each time node in the preset future time period of the preset load point according to the history voltage data of the corresponding moment of each time node in the preset future time period of the preset load point of the power distribution network;
the early warning subunit is used for giving an early warning result as normal when the predicted low voltage out-of-limit and the historical low voltage out-of-limit do not exist in the time node; otherwise, giving out an early warning result that the low voltage threshold crossing risk exists.
11. The system of claim 10, further comprising a tracking module;
the tracking module is used for ending the early warning process and waiting for the next early warning start if the early warning result is normal;
otherwise, issuing early warning information and tracking an early warning result;
the early warning information includes time nodes, lines, load nodes and voltage amplitudes for which low voltage violations are predicted.
12. The system of claim 11, wherein the tracking module comprises: a topology change subunit, a load change subunit and an invariant subunit;
the topology change subunit is used for carrying out low-voltage risk early warning again according to the latest load prediction data when the topology of the power distribution network changes, and if the early warning result is normal, canceling the early warning information and waiting for the next early warning start; otherwise, issuing early warning information and tracking an early warning result;
the load change subunit is used for predicting and starting an early warning process according to the latest load if the load changes when the topology of the power distribution network does not change, and canceling the early warning information, ending the early warning process and waiting for the next start if the early warning result is normal; otherwise, issuing early warning information and tracking an early warning result;
the invariant subunit is used for waiting until the early warning is carried out at the moment that the low voltage is out of limit when the topology and the load of the power distribution network are not changed, and canceling the early warning information if the low voltage is not out of limit; otherwise, the moment when the low voltage exceeds the limit and the voltage amplitude are obtained, and the early warning information is cancelled.
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