CN110970898B - Power grid low-voltage load shedding method and device considering dynamic voltage support strength - Google Patents
Power grid low-voltage load shedding method and device considering dynamic voltage support strength Download PDFInfo
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- CN110970898B CN110970898B CN201911239240.6A CN201911239240A CN110970898B CN 110970898 B CN110970898 B CN 110970898B CN 201911239240 A CN201911239240 A CN 201911239240A CN 110970898 B CN110970898 B CN 110970898B
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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
- H02J3/12—Circuit arrangements for ac mains or ac distribution networks for adjusting voltage in ac networks by changing a characteristic of the network load
- H02J3/14—Circuit arrangements for ac mains or ac distribution networks for adjusting voltage in ac networks by changing a characteristic of the network load by switching loads on to, or off from, network, e.g. progressively balanced loading
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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
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
- Y02B70/30—Systems integrating technologies related to power network operation and communication or information technologies for improving the carbon footprint of the management of residential or tertiary loads, i.e. smart grids as climate change mitigation technology in the buildings sector, including also the last stages of power distribution and the control, monitoring or operating management systems at local level
- Y02B70/3225—Demand response systems, e.g. load shedding, peak shaving
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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
- Y04S20/00—Management or operation of end-user stationary applications or the last stages of power distribution; Controlling, monitoring or operating thereof
- Y04S20/20—End-user application control systems
- Y04S20/222—Demand response systems, e.g. load shedding, peak shaving
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Abstract
The invention relates to a power grid low-voltage load shedding method considering dynamic voltage support strength, which comprises the following steps of: step 1: respectively calculating unit load short-circuit current of each node in the power grid; step 2: after voltage drop caused by faults in the power grid occurs, loads under corresponding nodes are sequentially cut off according to the sequence of unit load short-circuit current from small to large. The invention considers the actual conditions of different nodes in the power grid, so that the load shedding mode adopted when the voltage drops due to the reasons of faults and the like has certain pertinence, the judgment and the control are carried out according to the unit load short-circuit current under each node, and the improvement of the voltage recovery capability of the system is facilitated.
Description
Technical Field
The invention belongs to the field of power grid analysis and control, particularly relates to a low-voltage load shedding technology of a power grid, and particularly relates to a power grid low-voltage load shedding method and device considering dynamic voltage support strength.
Background
Along with the continuous expansion of the scale of the power grid, the gradual complexity of the network structure, the continuous increase of the unit capacity and load, the operation of the alternating current/direct current ultrahigh voltage equipment, the influence of economy and environment, and the universal adoption of a novel automatic control device, the power grid is enabled to be closer to the operation condition of the stability limit. Combining the above factors, there will be new challenges and problems to make the grid operate safely and stably.
The low-voltage load shedding is an important measure for maintaining safe, static and dynamic stability and economic operation of a power system and maintaining qualified power quality, and is the last defense line for safe and stable control in power operation. The method has important functions of ensuring the safety of the power grid after disturbance, avoiding heavy power failure and the like. However, the configuration scheme and setting method of low-pressure load shedding at present need to be perfected, and the optimization coordination strategy needs to be further researched.
Disclosure of Invention
The invention aims to provide a power grid low-voltage load shedding method considering dynamic voltage support strength, which aims at voltage drop caused by faults and is beneficial to improving the voltage recovery capability of a power grid system.
In order to achieve the purpose, the invention adopts the technical scheme that:
a power grid low-voltage load shedding method considering dynamic voltage support strength comprises the following steps:
step 1: respectively calculating unit load short-circuit current of each node in the power grid;
step 2: and after the voltage drops due to the faults in the power grid, sequentially cutting off the loads below the corresponding nodes according to the sequence of the unit load short-circuit current from small to large.
In the step 1, the method for calculating the unit load short-circuit current of the node comprises the following steps:
wherein the content of the first and second substances,
short-circuit current per unit load for the ith said node, IiFor short-circuit current of the ith node when short-circuit occurs, PiIs the active load under the ith node.
In the step 1, after the unit load short-circuit current of each node in the power grid is calculated respectively, the nodes are sorted according to the order from small to large of the unit load short-circuit current, and a sequence reflecting the voltage recovery weak point in the power grid is obtained.
In the step 1, calculating the unit load short-circuit current of each node in the power grid by adopting BPA software.
The invention also provides a power grid low-voltage load shedding device considering the dynamic voltage support strength, which is matched with the power grid low-voltage load shedding method considering the dynamic voltage support strength, and comprises the following components:
the unit load short-circuit current calculation module is used for calculating the unit load short-circuit current of each node in the power grid respectively;
the control module is connected with the unit load short-circuit current calculation module and used for obtaining the unit load short-circuit current of each node in the power grid through the unit load short-circuit current calculation module, and generating control signals for sequentially cutting off the loads below the corresponding nodes according to the sequence from small to large of the unit load short-circuit current after the voltage drops due to faults in the power grid;
and the load cutting module is respectively connected with the control module and the loads under the nodes and is used for sequentially cutting off the loads under the corresponding nodes according to the control signal and the sequence of the short-circuit current of the unit load from small to large.
In the unit load short-circuit current calculation module, the method for calculating the unit load short-circuit current of the node is as follows:
wherein the content of the first and second substances,
short-circuit current per unit load for the ith said node, IiFor short-circuit current of the ith node when short-circuit occurs, PiIs the active load under the ith node.
The unit load short-circuit current calculation module is loaded with BPA software for calculating the unit load short-circuit current of each node in the power grid.
The control module is further configured to, after the unit load short-circuit current of each node in the power grid is obtained, sort the nodes in the order from small to large of the unit load short-circuit current, and obtain a sequence reflecting a voltage recovery weak point in the power grid.
Due to the application of the technical scheme, compared with the prior art, the invention has the following advantages: the invention considers the actual situation of voltage support of different nodes in the power grid, so that the load shedding mode adopted when the voltage drops due to the reasons of faults and the like has certain pertinence, the judgment and the control are carried out according to the unit load short-circuit current under each node, and the improvement of the voltage recovery capability of the system is facilitated.
Drawings
Fig. 1 is a schematic block diagram of a power grid low-voltage load shedding device considering dynamic voltage support strength according to the present invention.
Fig. 2 is a graph of voltage recovery at node 1 in an embodiment of the present invention.
Fig. 3 is a graph of the voltage recovery at node 1 after load shedding in an embodiment of the present invention.
Detailed Description
The invention will be further described with reference to examples of embodiments shown in the drawings to which the invention is attached.
The first embodiment is as follows: a power grid low-voltage load shedding method considering dynamic voltage support strength comprises the following steps:
step 1: and respectively calculating the unit load short-circuit current of each node in the power grid.
In this step, the method for calculating the unit load short-circuit current of the node includes:
wherein the content of the first and second substances,
is unit load short-circuit current of ith nodeiFor short-circuit current at the i-th node when short-circuit occurs, PiIs the active load under the ith node. BPA software can be adopted to calculate the unit load short-circuit current of each node in the power grid.
After the unit load short-circuit current of each node in the power grid is calculated respectively, the nodes are sequenced according to the sequence of the unit load short-circuit current from small to large, and a sequence reflecting the voltage recovery weak point in the power grid is obtained.
Step 2: after voltage drop caused by faults in the power grid, loads under corresponding nodes are sequentially cut off according to the sequence of unit load short-circuit current from small to large.
As shown in fig. 1, the power grid low-voltage load shedding device considering dynamic voltage support strength for implementing the power grid low-voltage load shedding method considering dynamic voltage support strength includes a unit load short-circuit current calculation module, a control module and a load removal module.
And the unit load short-circuit current calculation module is used for calculating the unit load short-circuit current of each node in the power grid respectively. The control module is connected with the unit load short-circuit current calculation module and used for obtaining the unit load short-circuit current of each node in the power grid through the unit load short-circuit current calculation module, and generating control signals for sequentially cutting off the loads below the corresponding nodes according to the sequence from small to large of the unit load short-circuit current after voltage drop caused by faults in the power grid. The control module is further used for sequencing the nodes according to the sequence of the unit load short-circuit current from small to large after the unit load short-circuit current of each node in the power grid is obtained, and obtaining a sequence reflecting the voltage recovery weak point in the power grid. And the load cutting module is respectively connected with the control module and the loads under the nodes and is used for sequentially cutting off the loads under the corresponding nodes according to the control signal and the sequence from small to large of the short-circuit current of the unit load.
The unit load short-circuit current calculation module is loaded with BPA software for calculating the unit load short-circuit current of each node in the power grid, and the method for calculating the unit load short-circuit current of the node by using the BPA software comprises the following steps:
wherein the content of the first and second substances,
is unit load short-circuit current of ith nodeiFor short circuit of ith node when short circuit occursCurrent, PiIs the active load under the ith node.
The three-phase permanent metal short-circuit fault is a research object because the three-phase permanent metal short-circuit fault has the greatest impact on a power system and causes the most serious problems of safety and stability such as voltage drop and the like.
The magnitude of the short-circuit current is influenced by the power source layout and the geographical position thereof, particularly the electrical distance between a large-capacity power plant and a power plant group and a receiving end system or a load center, and the short-circuit current is larger when the node closer to the power plant is in a three-phase short circuit. On the other hand, voltages close to the power plant tend to have better voltage support. In view of this, it can be seen that the node short circuit current has a certain relationship with the dynamic voltage support strength.
However, the larger the short-circuit current of a node is, the larger the voltage supporting strength of the node cannot be said to be, and the load amount under the node may be larger. Therefore, the invention provides a concept of unit load short-circuit current, namely, the short-circuit current value is divided by the load under the node, and the recovery characteristic of the node voltage after the fault is measured by the unit load short-circuit current.
Considering the short-circuit current of all nodes of a receiving end system, and setting the number of the nodes to be analyzed in the system as NnodeWhen three-phase short circuit occurs at the ith node, the short-circuit current is IiThe active load at the node is PiThe calculation formula of the unit load short-circuit current is as follows:
the voltage recovery weak point in the system is determined according to the unit load short-circuit current, and then when the voltage drops due to the failure of the power grid, the load below the node is cut off in sequence from small to large according to the unit load short-circuit current of the voltage recovery weak point, so that the purpose of accelerating the voltage recovery after the failure is achieved.
On the basis, a small-start running mode of a certain power grid in winter of a certain year is taken as a case to carry out simulation verification in a BPA environment:
tables 1 and 2 are the integrated load model (SLM) parameters that were established using the statistical integrated load model software to account for the distribution network. Load parameters are added to the BPA card according to the data.
TABLE 1
| Rs | Xs | Xm | Rr | Xr | A | B | Tj | Motor ratio (%) |
| 0.0331 | 0.1095 | 2.9648 | 0.0192 | 0.11 | 0.6295 | 0 | 2.0372 | 65％ |
TABLE 2
| ZP％ | ZQ％ | IP％ | IQ％ | PP％ | PQ％ | R* | X* |
| 53 | 53 | 34 | 34 | 13 | 13 | 0.004 | 0.06 |
In order to detect the weak voltage recovery node in the power grid, the short-circuit current of all nodes in the system is calculated by BPA software, and the short-circuit current of a unit load is obtained by comparing the short-circuit current with the power load connected below the node.
10 nodes with the minimum unit load short-circuit current of the weak point of voltage recovery in the power grid are obtained through simulation experiments, the nodes are sorted from small to large as shown in a table 3, and the unit load short-circuit current of the system is continuously increased from the node 1 to the node 10.
According to the statistical data, the node with the minimum short-circuit current of the unit load in the system is taken as an example, and the influence of the three-phase short-circuit fault on the voltage recovery is intuitively sensed. Fig. 1 is a graph showing the voltage recovery of node 1 when the most influential line fails after the fault. As can be seen from the figure, the fault voltage recovery time of the node is longer, and the time for the voltage of the node to recover to 90% of the original voltage is 162 cycles.
TABLE 3
| Node point | Short-circuit current (kA) | Node load (MW) | Unit load short circuit current (kA/MW) |
| Node 1 | 54.584 | 458.2 | 0.11913 |
| Node 2 | 59.697 | 432.9 | 0.1379 |
| Node 3 | 58.427 | 413.5 | 0.1413 |
| Node 4 | 69.331 | 437.4 | 0.15851 |
| Node 5 | 54.419 | 331 | 0.16441 |
| Node 6 | 72.029 | 394 | 0.18281 |
| Node 7 | 55.668 | 241.4 | 0.2306 |
| Node 8 | 69.859 | 260 | 0.26869 |
| Node 9 | 57.016 | 165.5 | 0.34451 |
| Node 10 | 53.668 | 118.2 | 0.45404 |
After the weakest node of the voltage recovery is obtained according to the method, when the voltage drop is caused by the fault of the power grid, the load under the node is cut off in sequence from small to large according to the unit load short-circuit current of the weak point of the voltage recovery, so that the purpose of accelerating the voltage recovery after the fault is achieved.
And when a three-phase short-circuit fault occurs in the line, sequentially cutting off the load at the point according to the sequence from the node 1 to the node 10. Fig. 2 is a voltage recovery graph of the node 1 after a load shedding manner is adopted when a line with the largest influence is failed after the failure. As can be seen from the graph, the time taken for the node voltage at node 1 to recover to 90% of the original voltage is significantly reduced, and the time taken is 142 cycles. It can be seen from the figure that the low-voltage load shedding strategy provided by the invention considers two factors of short-circuit current and carried load of all nodes in the system, properly cuts off the load in the power grid and is beneficial to system voltage recovery.
The invention aims to provide a low-voltage load shedding strategy considering dynamic voltage support strength, which considers the short-circuit current of all nodes in a system and the load of the nodes, calculates the unit load short-circuit current under each node, and further sequences the unit load short-circuit current from low to high to obtain the weak point of voltage recovery. And when the system fails to cause voltage drop, sequentially cutting off the loads below the nodes according to the sequence of the voltage recovery weak points.
The invention has the advantages that:
(1) the invention considers the actual conditions of different nodes in the power grid, so that the load shedding mode adopted when the voltage drops due to the reasons of faults and the like has certain pertinence;
(2) compared with the method for judging the dynamic voltage supporting strength by simply using the short-circuit current, the method adds the load under each node, and judges by using the short-circuit current of the unit load;
(3) the invention is beneficial to improving the voltage recovery capability of the system.
The above embodiments are only for illustrating the technical idea and features of the present invention, and the purpose of the present invention is to enable those skilled in the art to understand the content of the present invention and implement the present invention, and not to limit the protection scope of the present invention by this means. All equivalent changes and modifications made according to the spirit of the present invention should be covered within the protection scope of the present invention.
Claims (6)
1. A power grid low-voltage load shedding method considering dynamic voltage support strength is characterized in that: the power grid low-voltage load shedding method considering the dynamic voltage support strength comprises the following steps of:
step 1: respectively calculating unit load short-circuit current of each node in the power grid;
step 2: after voltage drop caused by faults in the power grid occurs, sequentially cutting off loads under corresponding nodes according to the sequence of unit load short-circuit current from small to large;
in the step 1, the method for calculating the unit load short-circuit current of the node comprises the following steps:
wherein the content of the first and second substances,
is as followsiA unit load short-circuit current per one of the nodes,
is as followsiShort-circuit current of each of the nodes when short-circuit occurs,
is as followsiThe active load under each of the nodes.
2. The method for low-voltage load shedding of a power grid considering dynamic voltage support strength according to claim 1, wherein: in the step 1, after the unit load short-circuit current of each node in the power grid is calculated respectively, the nodes are sorted according to the order from small to large of the unit load short-circuit current, and a sequence reflecting the voltage recovery weak point in the power grid is obtained.
3. The method for low-voltage load shedding of a power grid considering dynamic voltage support strength according to claim 1, wherein: in the step 1, calculating the unit load short-circuit current of each node in the power grid by adopting BPA software.
4. The utility model provides a consider electric wire netting low pressure deloading device of dynamic voltage support intensity which characterized in that: the power grid low-voltage load shedding device considering the dynamic voltage support strength comprises:
the unit load short-circuit current calculation module is used for calculating the unit load short-circuit current of each node in the power grid respectively;
the control module is connected with the unit load short-circuit current calculation module and used for obtaining the unit load short-circuit current of each node in the power grid through the unit load short-circuit current calculation module, and generating control signals for sequentially cutting off the loads below the corresponding nodes according to the sequence from small to large of the unit load short-circuit current after voltage drop caused by faults in the power grid;
the load cutting module is respectively connected with the control module and the loads under the nodes and is used for sequentially cutting off the loads under the corresponding nodes according to the control signal and the sequence of the short-circuit current of the unit load from small to large;
in the unit load short-circuit current calculation module, the method for calculating the unit load short-circuit current of the node is as follows:
wherein, among others,
is as followsiEach of the sectionsThe unit load short-circuit current of the point,
is as followsiShort-circuit current of each of the nodes when short-circuit occurs,
is as followsiThe active load under each node.
5. The grid low-voltage load shedding device considering dynamic voltage support strength according to claim 4, wherein: the unit load short-circuit current calculation module is loaded with BPA software for calculating the unit load short-circuit current of each node in the power grid.
6. The grid low-voltage load shedding device considering dynamic voltage support strength according to claim 4, wherein: the control module is further configured to, after the unit load short-circuit current of each node in the power grid is obtained, sort the nodes in the order from small to large of the unit load short-circuit current, and obtain a sequence reflecting a voltage recovery weak point in the power grid.
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