CN114157018A - Distributed feeder automation recovery method based on line load rate and peer-to-peer communication - Google Patents
Distributed feeder automation recovery method based on line load rate and peer-to-peer communication Download PDFInfo
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- H—ELECTRICITY
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- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J13/00—Circuit arrangements for providing remote indication of network conditions, e.g. an instantaneous record of the open or closed condition of each circuitbreaker in the network; Circuit arrangements for providing remote control of switching means in a power distribution network, e.g. switching in and out of current consumers by using a pulse code signal carried by the network
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- 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
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- 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
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- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J13/00—Circuit arrangements for providing remote indication of network conditions, e.g. an instantaneous record of the open or closed condition of each circuitbreaker in the network; Circuit arrangements for providing remote control of switching means in a power distribution network, e.g. switching in and out of current consumers by using a pulse code signal carried by the network
- H02J13/00006—Circuit arrangements for providing remote indication of network conditions, e.g. an instantaneous record of the open or closed condition of each circuitbreaker in the network; Circuit arrangements for providing remote control of switching means in a power distribution network, e.g. switching in and out of current consumers by using a pulse code signal carried by the network characterised by information or instructions transport means between the monitoring, controlling or managing units and monitored, controlled or operated power network element or electrical equipment
- H02J13/00022—Circuit arrangements for providing remote indication of network conditions, e.g. an instantaneous record of the open or closed condition of each circuitbreaker in the network; Circuit arrangements for providing remote control of switching means in a power distribution network, e.g. switching in and out of current consumers by using a pulse code signal carried by the network characterised by information or instructions transport means between the monitoring, controlling or managing units and monitored, controlled or operated power network element or electrical equipment using wireless data transmission
- H02J13/00026—Circuit arrangements for providing remote indication of network conditions, e.g. an instantaneous record of the open or closed condition of each circuitbreaker in the network; Circuit arrangements for providing remote control of switching means in a power distribution network, e.g. switching in and out of current consumers by using a pulse code signal carried by the network characterised by information or instructions transport means between the monitoring, controlling or managing units and monitored, controlled or operated power network element or electrical equipment using wireless data transmission involving a local wireless network, e.g. Wi-Fi, ZigBee or Bluetooth
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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
- H02J2203/00—Indexing scheme relating to details of circuit arrangements for AC mains or AC distribution networks
- H02J2203/20—Simulating, e g planning, reliability check, modelling or computer assisted design [CAD]
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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
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
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- Y04S10/00—Systems supporting electrical power generation, transmission or distribution
- Y04S10/20—Systems supporting electrical power generation, transmission or distribution using protection elements, arrangements or systems
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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
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- Y04S40/00—Systems for electrical power generation, transmission, distribution or end-user application management characterised by the use of communication or information technologies, or communication or information technology specific aspects supporting them
- Y04S40/12—Systems for electrical power generation, transmission, distribution or end-user application management characterised by the use of communication or information technologies, or communication or information technology specific aspects supporting them characterised by data transport means between the monitoring, controlling or managing units and monitored, controlled or operated electrical equipment
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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
- Y04S40/00—Systems for electrical power generation, transmission, distribution or end-user application management characterised by the use of communication or information technologies, or communication or information technology specific aspects supporting them
- Y04S40/12—Systems for electrical power generation, transmission, distribution or end-user application management characterised by the use of communication or information technologies, or communication or information technology specific aspects supporting them characterised by data transport means between the monitoring, controlling or managing units and monitored, controlled or operated electrical equipment
- Y04S40/126—Systems for electrical power generation, transmission, distribution or end-user application management characterised by the use of communication or information technologies, or communication or information technology specific aspects supporting them characterised by data transport means between the monitoring, controlling or managing units and monitored, controlled or operated electrical equipment using wireless data transmission
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Abstract
The invention relates to a distributed feeder automation recovery method based on line load rate and peer-to-peer communication, which comprises the following steps: step 1, determining a fault section by adopting a synchronous sampling differential algorithm; step 2, outputting the information of the fault current to an intelligent power distribution terminal; step 3, removing faults; and 4, obtaining a fault recovery strategy suitable for the active power distribution network, and clearing the fault. According to the real-time load rate of the line, the invention formulates and generates a flexible fault recovery method, and improves the power supply recovery capability of the distributed FA.
Description
Technical Field
The invention belongs to the technical field of feeder automation of intelligent power distribution networks, and relates to a distributed feeder automation recovery method, in particular to a distributed feeder automation recovery method based on line load rate and peer-to-peer communication.
Background
The feeder automation technology is used as an important technical means for improving the power supply reliability of a power grid, after a distribution network fails, under the condition that no manual intervention or a small amount of manual intervention is needed, the feeder automation technology can quickly position a fault section and isolate the power supply recovery of the fault section and a non-fault section, can effectively reduce the power failure time of the distribution network, further improves the power supply reliability, and is widely applied to the current power distribution network. Along with the increasing requirement of users on power supply reliability, the intelligent distributed FA relies on a 5G communication network to start feeder automation to perform fault processing, and completes accurate positioning, fault judgment, isolation and power restoration of a non-fault section of a distribution network line section by utilizing intercommunication, protection coordination and time sequence coordination among intelligent terminals, so that rapid isolation and self-healing of faults are realized. The existing technical scheme of the fault recovery strategy is that firstly, the connection relation and the switch position in a power distribution network and the structure of the network after the change are identified through system modeling and topology analysis; and then, by setting a plurality of fault modes and fault numbers, and protecting equipment faults and other situations, the main station and the distributed FLISR are detected to obtain a fault recovery strategy.
The specific implementation mode is as follows: firstly, a fault recovery strategy is calculated through mathematical model modeling, for example, a quadratic programming load model of a power distribution network is built for a system in stages, and a recursive quadratic programming solution is adopted to solve a fault recovery problem; the other method is to generate a more reliable recovery scheme with the past experience, for example, an expert system is adopted, and expert knowledge of power distribution network fault recovery can be converted into a rule base and reasoning knowledge of the expert system, so that a safe and reliable power supply recovery scheme is formed.
However, when a power distribution network fails, the fault recovery strategy provided by the above technical scheme has the defects of singleness, fixation and the like, and due to the fact that the number of distributed FA terminals in the power distribution network is large, the distribution range is wide, and only the adjacency relation of adjacent terminals is known, a fixed switch is generally specified to be closed after fault isolation so as to recover the power supply of a non-fault area, and a flexible fault recovery strategy cannot be formulated and generated according to the real-time load rate of a line.
Through searching, no prior art publication which is the same as or similar to the present invention is found.
Disclosure of Invention
The invention aims to overcome the defects of the prior art, provides a distributed feeder automation recovery method based on line load rate and peer-to-peer communication, and solves the problems that the existing method for recovering faults is single and fixed, and the existing recovery method is not comprehensive and flexible.
The invention solves the practical problem by adopting the following technical scheme:
a distributed feeder automation recovery method based on line load rate and peer-to-peer communication comprises the following steps:
step 1, when a line of an active power distribution network has a fault, determining a fault section by adopting a differential algorithm of synchronous sampling;
and 4, after the fault is removed in the step 3, transferring the load at the feeder line where the fault is located according to the line load rate, and recursively calculating the switching information of each switch to enable the downstream power supply area to enter a fault recovery stage according to the residual loaded power supply capacity in the non-fault area so as to finally obtain a fault recovery strategy suitable for the active power distribution network and remove the fault.
Further, the specific steps of step 1 include:
(1) determining whether an overcurrent fault signal appears on the outlet switch, if so, protecting tripping, and starting a differential algorithm to determine a fault area; meanwhile, the outgoing switch communicates with the adjacent switch and transmits a current waveform and an overcurrent signal;
(2) it is determined whether an overcurrent phenomenon occurs in two adjacent switches. If yes, going to the next step; if the switch on one side of the feeder line has overcurrent and the other side has no overcurrent, the fault is positioned between two ends of the feeder line, and the switches need to be disconnected; if neither switch has an overcurrent, the fault is not in the feeder;
(3) current waveform through two switches adjacent before and after a fault, I1R，I1I，I2R，I2IMay be formed by1＝tg-1(I1R/I1I) And theta2＝tg-1(I2R/I2I) Calculating to obtain; the phase angle can be calculated by the fault current waveform sampled from both ends of the line; judging and isolating a fault area through current waveforms and phase angle information of two adjacent switches before and after a fault, and if theta is greater than or equal to1-θ2I belongs to (180-delta, 180-delta + delta), delta is an actual error coefficient and simultaneously considers the current phase fluctuation caused by the capacitance of the line pair to the ground; the fault is located within this feeder part; otherwise, other adjacent switches will be sought;
the formula for calculating the fault current phase angle through the fault current waveform sampled from two ends of the line is as follows:
therefore, the position of the fault can be deduced from the current amplitudes I1 and I2 and different line end phase angles;
(4) and (4) continuously searching for the adjacent switch at the downstream and repeating the step (2) and the step (3) until a fault area is found, and locking the specific position of the fault area.
Further, the specific steps of step 2 include:
(1) the 5G communication module obtains system information. The 5G communication module obtains a static topology model, a dynamic topology model and the overcurrent signal information calculated in the step 1 and obtained by the current acquisition module;
(2) and self-detecting the communication state. In the communication process, the intelligent distributed FA terminal can perform self-detection on the 5G communication state, and obtains required information to the intelligent power distribution terminal by adopting different logic receiving methods according to the current communication system state. Entering the step (3) when the communication system is in a good state, and entering the step (4) if the communication system is not in a good state;
(3) when the 5G wireless communication system is normal, the 5G communication module sends the overcurrent information of the fault position and the fault position information to the adjacent feeder line intelligent terminals in a message mode, receives current detection information from the downstream switch and realizes information exchange between the intelligent power distribution terminals at the adjacent switches.
(4) When the 5G system is busy for a short time, the number of received replies in the time of the newly sent topology message is reduced; if the communication quality is reduced to be less than the minimum value, the system dynamically updates the time according to the current communication quality information, so that the waiting time of the distributed FA terminal is increased by 10%; the process of increasing the waiting time can be periodically and repeatedly executed, so that the terminal can receive enough information, the current fault message can be successfully sent, the current detection information from the downstream switch is received, and the adjacent switch can acquire the information of the positioning fault area.
Further, the specific steps of step 3 include:
(1) detecting the short-circuit current at the position of the DER in the power distribution network according to the position information of the overcurrent switch transmitted in the step 2, if the DER outlet current is small and cannot capture an overcurrent signal on the DG side switch, executing the step (2), and if not, executing the step (3);
(2) the upstream and downstream switches of the current fault position and the switches of other distributed power supplies connected to the power distribution network have no overcurrent, and a differential protection algorithm in the step 1 is adopted to start a differential algorithm to determine a fault area;
(3) since the DER can provide short-circuit current to the short-circuit point, so that overcurrent can be detected at the switch upstream or downstream of the fault position, the differential protection algorithm in step 1 is started to solve the similar fault location problem that the short-circuit fault occurs upstream of one DER or downstream of one DER;
(4) and activating a starting protection condition according to the positioned fault position information, disconnecting the switches at the upstream and downstream of the fault position, and removing the fault to realize the isolation of the fault.
Moreover, the specific method of the step 4 is as follows:
(1) after the fault is isolated in the step 3, the downstream switch of the fault outlet switch sends out a fault signal, and carries out communication check with the adjacent switch in a peer-to-peer communication mode to search for a tie switch;
(2) after the interconnection switch is determined, transferring the load of the feeder line where the fault is located according to the line load rate, judging the residual on-load power supply capacity in the non-fault area, and determining the opening and closing information of the interconnection switch group according to the relation among the power supply capacity of the power supply feeder line, the load of the power loss area and the capacity of the DER in the area;
(3) and judging whether the recovery strategy can meet the loss capacity or not according to the opening and closing information of the interconnection switch group, finally obtaining a fault recovery strategy suitable for the active power distribution network, and clearing the fault.
The invention has the advantages and beneficial effects that:
the invention discloses a Distributed Feeder Automation (FA) recovery method based on line load rate and peer-to-peer communication, which is characterized in that after a power distribution network fails, according to current waveforms before and after the failure, the position of the failure is deduced from current amplitude and phase angles at different line ends through a synchronous sampling differential algorithm, the isolation of the failure is realized through a short-circuit current signal provided by Distributed Energy Resources (DER) and the magnitude of outlet current at the failure position, when one Feeder outlet switch is tripped by the failure, a downstream switch of the outlet switch sends out a failure signal, and the communication check is carried out with adjacent switches in a peer-to-peer communication mode to search for a contact switch. And each intelligent power distribution terminal judges the electrical section where the fault occurs according to the fault current information detected by the monitoring switch and the fault current information received from the intelligent power distribution terminal at the downstream switch. At the moment, the load of the fault feeder line area is completely supplied with power by the other feeder line, the relation between the load in the area and the residual loaded power supply capacity is calculated according to the relation between the power supply capacity of the power supply feeder line and the load of the power loss area and the capacity difference of the DER in the area, a distributed fault location, isolation and service restoration (FLISR) strategy is worked out according to the relation, a switch which cannot be met is set as a new disconnected connection switch, the area to be supplied with power in the lower reaches enters the fault restoration stage of the algorithm again for calculation, and finally the fault restoration strategy suitable for the active power distribution network is obtained. The method formulates and generates a flexible fault recovery method according to the real-time load rate of the line, and improves the power supply recovery capability of the distributed FA.
Drawings
FIG. 1 is a schematic diagram of the fault recovery of the present invention;
FIG. 2 is a schematic diagram of the differential protection algorithm of the present invention;
figure 3 is a schematic diagram of the ADN of the present invention.
Detailed Description
The embodiments of the invention will be described in further detail below with reference to the accompanying drawings:
a distributed feeder automation recovery method based on line load rate and peer-to-peer communication, as shown in fig. 1, includes the following steps:
step 1: when the active power distribution network line has a fault, determining a fault section by adopting a differential algorithm of synchronous sampling;
the specific method of the step 1 comprises the following steps:
when the active power distribution network line has a fault, capacitive currents at two ends of a fault point are calculated and compared by adopting a synchronous sampling differential algorithm, a waveform curve of the fault current is reduced through a first-order low-pass filter, then a current phase angle after the fault occurs is calculated through a 0.5s current waveform before the switch trips, and finally a fault area is searched according to the relation of the current phase angle.
As shown in fig. 2, the specific steps of step 1 include:
(1) determining whether an overcurrent fault signal appears on the outlet switch, if so, protecting tripping, and starting a differential algorithm to determine a fault area; at the same time, the outgoing switch communicates with the adjacent switch and transmits a current waveform and an over-current signal.
(2) It is determined whether an overcurrent phenomenon occurs in two adjacent switches. If yes, going to the next step; if the switch on one side of the feeder line has overcurrent and the other side has no overcurrent, the fault is positioned between two ends of the feeder line, and the switches need to be disconnected; if neither switch is over-current, the fault is not in the feeder.
(3) Current waveform through two switches adjacent before and after a fault, I1R，I1I，I2R，I2IMay be formed by1＝tg-1(I1R/I1I) And theta2＝tg-1(I2R/I2I) Calculating to obtain; the phase angle can be calculated by the fault current waveform sampled from both ends of the line; judging and isolating a fault area through current waveforms and phase angle information of two adjacent switches before and after a fault, and if theta is greater than or equal to1-θ2I belongs to (180-delta, 180-delta + delta), delta is an actual error coefficient and simultaneously considers the current phase fluctuation caused by the capacitance of the line pair to the ground; the fault is located within this feeder part; otherwise, other adjacent switches will be sought;
the formula for calculating the fault current phase angle through the fault current waveform sampled from two ends of the line is as follows:
the position of the fault can thus be deduced from the current amplitudes I1, I2 and the different line end phase angles. A schematic diagram of the differential algorithm is shown in fig. 2.
(4) And (4) continuously searching for the adjacent switch at the downstream and repeating the step (2) and the step (3) until a fault area is found, and locking the specific position of the fault area.
in this embodiment, in the communication process, the intelligent distributed FA terminal may perform self-detection on the 5G communication state, and transmit and obtain required information by using different logic reception methods according to the current communication system state.
The specific steps of the step 2 comprise:
(1) the 5G communication module obtains system information. The 5G communication module obtains a static topology model, a dynamic topology model and the overcurrent signal information calculated in the step 1 and obtained by the current acquisition module;
(2) and self-detecting the communication state. In the communication process, the intelligent distributed FA terminal can perform self-detection on the 5G communication state, and obtains required information to the intelligent power distribution terminal by adopting different logic receiving methods according to the current communication system state. Entering the step (3) when the communication system is in a good state, and entering the step (4) if the communication system is not in a good state;
(3) when the 5G wireless communication system is normal, the 5G communication module sends the overcurrent information of the fault position and the fault position information to the adjacent feeder line intelligent terminals in a message mode, receives current detection information from the downstream switch and realizes information exchange between the intelligent power distribution terminals at the adjacent switches.
(4) When the 5G system is busy for a short time, the number of received replies in the time of the newly transmitted topology message is reduced. If the communication quality is reduced to be less than the minimum value, the system dynamically updates the time according to the current communication quality information, so that the waiting time of the distributed FA terminal is increased by 10%. The above-mentioned process of increasing the waiting time may be repeated periodically to ensure that the terminal can receive enough information. The current fault message can be successfully sent, and the current detection information from the downstream switch is received, so that the adjacent switches can acquire the information of the positioning fault area.
In the step 2, in a multi-connection and multi-section multi-power-supply distribution network connection mode, according to the distributed FA processing method provided by the invention, when one feeder outlet switch is tripped due to a fault, a downstream switch of the outlet switch sends a fault signal, and performs communication check with an adjacent switch in a peer-to-peer communication mode to find an interconnection switch.
In this embodiment, when feeder automation intelligent terminals communicate with each other, the distributed current information exchanges information between the intelligent power distribution terminal and the intelligent power distribution terminal at an adjacent switch through a peer-to-peer communication network, and each intelligent power distribution terminal determines whether a fault occurs in an electrical section between the monitoring switch and a downstream switch according to fault current information detected at its monitoring switch and information received from the intelligent power distribution terminal at the downstream switch as to whether the fault current is detected.
And 3, after receiving the fault current information in the step 2, the intelligent power distribution terminal judges the fault occurrence situation according to whether the island protection is started and whether the DER provides short-circuit current during the fault in the area where the fault is located, and starts a protection condition after activating the outlet protection of the fault to remove the fault.
The specific steps of the step 3 comprise:
(1) detecting the short-circuit current at the position of the DER in the power distribution network according to the position information of the overcurrent switch transmitted in the step 2, if the DER outlet current is small and cannot capture an overcurrent signal on the DG side switch, executing the step (2), and if not, executing the step (3);
(2) and (3) the upstream and downstream switches of the current fault position and the switches of other distributed power supplies connected to the power distribution network have no overcurrent, and the differential protection algorithm in the step 1 is adopted to start a differential algorithm to determine the fault area.
(3) Since the DER can provide short-circuit current to the short-circuit point, so that overcurrent can be detected at the switch upstream or downstream of the fault location, the differential protection algorithm in step 1 initiates to solve similar fault localization problems where a short-circuit fault occurs upstream of one DER or downstream of one DER.
(4) And activating a starting protection condition according to the positioned fault position information, disconnecting the switches at the upstream and downstream of the fault position, and removing the fault to realize the isolation of the fault.
In this embodiment, for an Active Distribution Network (ADN) system including a large number of DERs (DER), the following three situations may occur when a fault occurs:
1) islanding protection for all distributed power sources is not enabled.
2) And (4) starting island protection of part of the distributed power supply.
3) All distributed power island protection is started.
According to the Distributed Generator (DG) capacity and the outlet current during a fault in the above three cases. The protection measures are initiated by the detected over-current signal information, which is activated by the over-current signal at the outlet switch when the system DG capacity may be small and the outlet current during a fault may be small to not capture the over-current signal on the DG side switch.
The start-up protection condition is activated by an over-current signal at the outlet switch according to a differential protection algorithm.
And 4, step 4: and 3, after the fault is removed in the step 3, transferring the load at the feeder line where the fault is located according to the line load rate, and recursively calculating the switching information of each switch to a downstream switch according to the residual loaded power supply capacity in the non-fault area to enable the downstream area to be supplied with power to enter a fault recovery stage, so as to finally obtain a fault recovery strategy applicable to the active power distribution network and remove the fault.
The specific method of the step 4 comprises the following steps:
(1) after the fault is isolated in step 3, the downstream switch of the fault outlet switch sends out a fault signal, and performs communication check with the adjacent switch in a peer-to-peer communication mode to find the tie switch.
(2) After the interconnection switch is determined, transferring the load of the feeder line where the fault is located according to the line load rate, judging the residual on-load power supply capacity in the non-fault area, and determining the opening and closing information of the interconnection switch group according to the relation among the power supply capacity of the power supply feeder line, the load of the power loss area and the capacity of the DER in the area;
(3) and judging whether the recovery strategy can meet the loss capacity or not according to the opening and closing information of the interconnection switch group, finally obtaining a fault recovery strategy suitable for the active power distribution network, and clearing the fault.
And for the feeder line with the fault, judging whether the recovery strategy can meet the loss capacity according to an algorithm of the interconnection switch group, and calculating whether the load in the area can meet the residual on-load power supply capacity according to the load of the feeder line providing the power supply capacity and the power loss area and the capacity difference of the DER in the area. If so, the recursive computation continues with the downstream switch under the FLISR policy until it fails. And then, setting the switch which cannot meet the requirement as a disconnected new connection switch, so that the downstream power supply area to be supplied reenters the fault recovery stage of the algorithm for calculation, and finally obtaining the fault recovery strategy suitable for the active power distribution network.
In this embodiment, for a feeder line with a fault, whether a recovery strategy can meet the loss capacity is judged according to an algorithm of a tie switch group, and a fault recovery strategy suitable for an active power distribution network is obtained according to the load of the feeder line providing the power supply capacity and a power loss area and the capacity difference of a DER in the area. In multi-connection and multi-branch distribution networks, IEEE 1547 and 2003 stipulate that DERs cannot supply power as isolated islands after accessing the distribution network. In this case, the DER connected to the circuit breaker can only be seen as a load switch for the power distribution system rather than a current breaker. Thus, DER cannot be considered as a new power point in the distribution network during fault recovery, but only as a negative power load in a conventional multi-connection multi-branch distribution network. And for the three cases in the step 3, obtaining a distributed processing FLISR strategy according to the loads of a feeder line providing power supply capacity and a power loss area and the capacity difference of DER in the area.
In a multi-connection and multi-section multi-power-supply distribution network connection mode, according to the distributed processing method provided by the invention, when one feeder outlet switch is tripped due to a fault, a downstream switch of the outlet switch sends a fault signal, and the communication check is carried out with an adjacent switch in a peer-to-peer communication mode to find a connection switch. The load in this feeder area will now be supplied entirely by the other feeder. And if the power supply capacity of the power supply feeder is smaller than the difference between the load of the power loss area and the volume of the DER in the area, namely assuming the DER as a load, and calculating whether the load in the area can meet the residual on-load power supply capacity. If so, the recursive computation continues with the downstream switch until it fails. And then, setting the switch which cannot meet the requirement as a disconnected new connection switch, so that the downstream power supply area to be supplied reenters the fault recovery stage of the algorithm for calculation, and finally obtaining the fault recovery strategy suitable for the active power distribution network.
In this embodiment, in step 4, for a feeder line with a fault, whether the recovery strategy can meet the loss capacity is determined according to an algorithm of a tie switch group, and a fault recovery strategy applicable to the active power distribution network is obtained according to a load of the feeder line providing the power supply capacity to the feeder line and the power loss area and a capacity difference of the DER in the area. In multi-connection and multi-branch distribution networks, IEEE 1547 and 2003 stipulate that DERs cannot supply power as isolated islands after accessing the distribution network. In this case, the DER connected to the circuit breaker can only be seen as a load switch for the power distribution system rather than a current breaker. Thus, DER cannot be considered as a new power point in the distribution network during fault recovery, but only as a negative power load in a conventional multi-connection multi-branch distribution network.
And the load in the feeder line area with the fault is supplied with power by the other feeder line, and the power supply recovery strategy is obtained by recursively calculating the power supply capacity of the power supply feeder line, the load of the power loss area and the capacity difference of the DER in the area.
The specific implementation process is illustrated by the system shown in fig. 3. In this active power distribution grid system, a fault has occurred between the load switches 4 and 5. Two distributed energy sources are connected to the power distribution network through switches 3 and 6, respectively, and the connection of the two distributed energy sources changes the distribution of short-circuit current. The circuit breaker 1 in fig. 3 is a feeder outlet switch. The switch 7 is a tie switch. When a fault occurs, the following three situations may occur:
1) islanding protection for all distributed power sources is not enabled.
2) And (4) starting island protection of part of the distributed power supply.
3) All distributed power island protection is started.
Although the Distributed Generator (DG) capacity to access the ADN may be small and the outlet current during a fault may be small to not capture the overcurrent signal on the DG side switches, protection may be activated simply by the overcurrent signal at the outlet switches without the need for a voltage loss signal at each switch. Because the present invention employs a distributed FA process and conditions will be initiated after the failed egress protection is activated. Therefore, the differential protection proposed in step 1 is applicable to the above three cases, specifically as follows:
1) case 1: DER provides short circuit current to the short circuit point, so switches 3, 5 and 6 are over current, which conventional feeder automation cannot handle. The differential protection algorithm proposed in step 1 of the present invention can solve similar fault localization problems where a short-circuit fault occurs upstream of a DER or downstream of a DER. Assuming that the protection in the feeder outlet circuit breaker is the current fast trip protection of 0s, the distributed processing FLISR strategy of ADN is given in table 1 according to the difference between the feeder supply capacity and the load of the power loss area and the capacity of DER in the area.
TABLE 1 situation 1 AND schematic
2) Case 2: when the DER at switch 3 provides a short circuit current and the DER at switch 6 cannot provide a short circuit current, switch 3 is over current and switches 5 and 6 are not over current. Or DER at switch 6 provides a short circuit current and DER at switch 3 does not provide a short circuit current, when switches 5 and 6 are in an overcurrent state and switch 3 is not overcurrent. Both cases can be solved by the proposed differential protection algorithm. We select a case where DER at switch 3 provides short circuit current and DER at switch 6 cannot. The detailed strategy of FLISR is given in Table 2 according to the difference between the power supply capacity provided by the feeder line and the load of the power loss area and the volume of DER in the area.
TABLE 2 AND schematic in case 2
3) Case 3: no DER provides the short circuit current. At this time, none of the switches 3, 5 and 6 is over-current. At the moment, the fault condition is the same as that of the traditional distribution network, the traditional feeder automation can process the fault condition, and the differential protection algorithm provided by the invention is also effective. At this time, according to the difference between the power supply capacity provided by the feeder line and the load of the power loss area and the capacity of DER in the area, the distributed processing FLISR strategy of the ADN is shown in Table 3.
TABLE 3 AND schematic for case 3
By the aid of the distributed processing FLISR strategy, for a feeder line with a fault, according to the load of the feeder line providing power supply capacity for the feeder line and a power loss area and the capacity difference of DER in the area, whether the load in the area can meet the residual on-load power supply capacity of the feeder line can be calculated. If so, the recursive computation continues with the downstream switch under the FLISR policy until it fails. And then, setting the switch which cannot meet the requirement as a disconnected new connection switch, so that the downstream power supply area to be supplied reenters the fault recovery stage of the algorithm for calculation, and finally obtaining the fault recovery strategy suitable for the active power distribution network. The fault recovery strategy based on the line load rate judges whether the recovery strategy can meet the loss capacity according to the algorithm of the interconnection switch group. Failure recovery of ADN is achieved by the above process, as shown in fig. 1.
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.
Claims (5)
1. A distributed feeder automation recovery method based on line load rate and peer-to-peer communication is characterized in that: the method comprises the following steps:
step 1, when a line of an active power distribution network has a fault, determining a fault section by adopting a differential algorithm of synchronous sampling;
step 2, based on the fault section determined in the step 1, fault current waveforms before and after the line fault are mutually transmitted in a peer-to-peer communication mode, and information of the fault current is output to the intelligent power distribution terminal;
step 3, after receiving the fault current information in the step 2, the intelligent power distribution terminal judges the fault occurrence situation according to whether the island protection is started and whether the DER provides short-circuit current during the fault of the area where the fault is located, and starts a protection condition after activating the outlet protection of the fault to remove the fault;
and 4, after the fault is removed in the step 3, transferring the load at the feeder line where the fault is located according to the line load rate, and recursively calculating the switching information of each switch to enable the downstream power supply area to enter a fault recovery stage according to the residual loaded power supply capacity in the non-fault area so as to finally obtain a fault recovery strategy suitable for the active power distribution network and remove the fault.
2. The method of claim 1, wherein the distributed feeder automation recovery method based on line load rate and peer-to-peer communication comprises: the specific steps of the step 1 comprise:
(1) determining whether an overcurrent fault signal appears on the outlet switch, if so, protecting tripping, and starting a differential algorithm to determine a fault area; meanwhile, the outgoing switch communicates with the adjacent switch and transmits a current waveform and an overcurrent signal;
(2) it is determined whether an overcurrent phenomenon occurs in two adjacent switches. If yes, going to the next step; if the switch on one side of the feeder line has overcurrent and the other side has no overcurrent, the fault is positioned between two ends of the feeder line, and the switches need to be disconnected; if neither switch has an overcurrent, the fault is not in the feeder;
(3) current waveform through two switches adjacent before and after a fault, I1R，I1I，I2R，I2IMay be formed by1＝tg-1(I1R/I1I) And theta2＝tg-1(I2R/I2I) Calculating to obtain; the phase angle can be calculated by the fault current waveform sampled from both ends of the line; judging and isolating a fault area through current waveforms and phase angle information of two adjacent switches before and after a fault, and if theta is greater than or equal to1-θ2I belongs to (180-delta, 180-delta + delta), delta is an actual error coefficient and simultaneously considers the current phase fluctuation caused by the capacitance of the line pair to the ground; the fault is located within this feeder part; otherwise, other adjacent switches will be sought;
the formula for calculating the fault current phase angle through the fault current waveform sampled from two ends of the line is as follows:
therefore, the position of the fault can be deduced from the current amplitudes I1 and I2 and different line end phase angles;
(4) and (4) continuously searching for the adjacent switch at the downstream and repeating the step (2) and the step (3) until a fault area is found, and locking the specific position of the fault area.
3. The method of claim 1, wherein the distributed feeder automation recovery method based on line load rate and peer-to-peer communication comprises: the specific steps of the step 2 comprise:
(1) the 5G communication module obtains system information. The 5G communication module obtains a static topology model, a dynamic topology model and the overcurrent signal information calculated in the step 1 and obtained by the current acquisition module;
(2) and self-detecting the communication state. In the communication process, the intelligent distributed FA terminal can perform self-detection on the 5G communication state, and obtains required information to the intelligent power distribution terminal by adopting different logic receiving methods according to the current communication system state. Entering the step (3) when the communication system is in a good state, and entering the step (4) if the communication system is not in a good state;
(3) when the 5G wireless communication system is normal, the 5G communication module sends the overcurrent information of the fault position and the fault position information to the adjacent feeder line intelligent terminals in a message mode, receives current detection information from the downstream switch and realizes information exchange between the intelligent power distribution terminals at the adjacent switches.
(4) When the 5G system is busy for a short time, the number of received replies in the time of the newly sent topology message is reduced; if the communication quality is reduced to be less than the minimum value, the system dynamically updates the time according to the current communication quality information, so that the waiting time of the distributed FA terminal is increased by 10%; the process of increasing the waiting time can be periodically and repeatedly executed, so that the terminal can receive enough information, the current fault message can be successfully sent, the current detection information from the downstream switch is received, and the adjacent switch can acquire the information of the positioning fault area.
4. The method of claim 1, wherein the distributed feeder automation recovery method based on line load rate and peer-to-peer communication comprises: the specific steps of the step 3 comprise:
(1) detecting the short-circuit current at the position of the DER in the power distribution network according to the position information of the overcurrent switch transmitted in the step 2, if the DER outlet current is small and cannot capture an overcurrent signal on the DG side switch, executing the step (2), and if not, executing the step (3);
(2) the upstream and downstream switches of the current fault position and the switches of other distributed power supplies connected to the power distribution network have no overcurrent, and a differential protection algorithm in the step 1 is adopted to start a differential algorithm to determine a fault area;
(3) since the DER can provide short-circuit current to the short-circuit point, so that overcurrent can be detected at the switch upstream or downstream of the fault position, the differential protection algorithm in step 1 is started to solve the similar fault location problem that the short-circuit fault occurs upstream of one DER or downstream of one DER;
(4) and activating a starting protection condition according to the positioned fault position information, disconnecting the switches at the upstream and downstream of the fault position, and removing the fault to realize the isolation of the fault.
5. The method of claim 1, wherein the distributed feeder automation recovery method based on line load rate and peer-to-peer communication comprises: the specific method of the step 4 comprises the following steps:
(1) after the fault is isolated in the step 3, the downstream switch of the fault outlet switch sends out a fault signal, and carries out communication check with the adjacent switch in a peer-to-peer communication mode to search for a tie switch;
(2) after the interconnection switch is determined, transferring the load of the feeder line where the fault is located according to the line load rate, judging the residual on-load power supply capacity in the non-fault area, and determining the opening and closing information of the interconnection switch group according to the relation among the power supply capacity of the power supply feeder line, the load of the power loss area and the capacity of the DER in the area;
(3) and judging whether the recovery strategy can meet the loss capacity or not according to the opening and closing information of the interconnection switch group, finally obtaining a fault recovery strategy suitable for the active power distribution network, and clearing the fault.
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