CN113809742A - Method and system for dividing micro-grid of small hydropower station island after fault - Google Patents
Method and system for dividing micro-grid of small hydropower station island after fault Download PDFInfo
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- CN113809742A CN113809742A CN202111133669.4A CN202111133669A CN113809742A CN 113809742 A CN113809742 A CN 113809742A CN 202111133669 A CN202111133669 A CN 202111133669A CN 113809742 A CN113809742 A CN 113809742A
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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
- H02J3/001—Methods to deal with contingencies, e.g. abnormalities, faults or failures
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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
- H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
- H02J3/388—Islanding, i.e. disconnection of local power supply from the network
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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
- H02J2203/10—Power transmission or distribution systems management focussing at grid-level, e.g. load flow analysis, node profile computation, meshed network optimisation, active network management or spinning reserve management
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Abstract
The invention discloses a method and a system for dividing a micro-grid of a small hydropower station island after a fault, wherein the method comprises the following steps: s1, after a fault occurs, judging whether the line is located at the upstream or the downstream of the fault point by a feeder automation terminal FTU of each line of the small hydropower island micro-grid according to fault characteristic information; s2, if the feeder automation terminal FTU of each line of the small hydropower island microgrid judges that the line is located at the downstream of the fault point, the line enters an island state, and island division is started; s3, after the island division is started, disconnecting each isolating switch at the downstream of the fault according to the magnitude of the current at the two sides before the fault according to the timing characteristic; and S4, the feeder automation terminals FTUs in the circuit are successively disconnected according to the timing characteristic, and the operation is stopped until the feeder automation terminals FTUs detect all fault characteristic quantities, so that a plurality of stably-operating island micro-grids are formed. The invention has the advantages of high speed of forming the stable island, reduction of fault recovery time and reduction of unnecessary load loss.
Description
Technical Field
The invention relates to the technical field of power system fault recovery, in particular to a method and a system for dividing a micro-grid of a small hydropower station island after a fault.
Background
With the increasing prominence of energy crisis and environmental problems, small hydropower stations are widely applied to power distribution networks in mountainous areas and rural areas as a distributed power source with dispersibility, simplicity and flexibility. A large number of small hydropower stations are connected into the power distribution network, so that the operation characteristics of the power grid are changed while the environmental deterioration is reduced and various problems of the traditional power grid are solved, and the challenge is brought to the safe and stable operation of the power grid. Because the lines of the small hydropower microgrid are usually distributed in a radiation mode, when a short-circuit fault occurs at a certain point in a branch, the line at the downstream of the fault point can enter an island state. The mountainous area and rural area where the small hydropower is distributed more have rich hydraulic resources but less load consumption, so the small hydropower microgrid belongs to a typical power delivery system. If the small hydropower micro-grid enters an island mode and cannot transmit excessive power to a large power grid, instability of frequency and voltage in the island can be caused, and even island disconnection can be caused. Therefore, designing a reliable islanding strategy after the small hydropower station microgrid fails is of great significance.
The existing small hydropower station micro-grid division methods mainly comprise two methods. The first method is that when a Feeder Terminal (FTU) of each line of the small hydropower microgrid detects a fault, each isolating switch in the small hydropower microgrid is sequentially disconnected from the tail end of the line until the FTU cannot detect the fault amount; the second method is that after a feeder automation terminal FTU detects that a fault occurs, all isolating switches in the small hydropower microgrid are firstly disconnected, then reclosing is sequentially carried out from the head end of the line, and if the fault section is reclosed, the switch of the fault section is disconnected again, and reclosing is stopped. Since both of the above methods ensure the selectivity by using the operation delay, the time consumption is long, and the excessive load which does not need to be removed is easily cut off. In summary, it is necessary to develop a method for fault islanding of a small hydropower microgrid, which is fast in operation and can reduce the number of removed loads to the maximum.
Disclosure of Invention
In order to solve the technical problems in the prior art, the invention provides a method and a system for dividing a microgrid of a small hydropower station island after a fault.
The method is realized by adopting the following technical scheme: a method for dividing a micro-grid of a small hydropower station island after a fault comprises the following steps:
s1, after a fault occurs, judging whether the line is located at the upstream or the downstream of the fault point by a feeder automation terminal FTU of each line of the small hydropower island micro-grid according to fault characteristic information;
s2, if the feeder automation terminal FTU of each line of the small hydropower island microgrid judges that the line is located at the upstream of a fault point, the line cannot enter an island state, and island division is not started; if the line is located at the downstream of the fault point, the line enters an island state, island division is started, and the step S3 is entered;
s3, after the island division is started, disconnecting each isolating switch at the downstream of the fault according to the magnitude of the current at the two sides before the fault according to the timing characteristic;
and S4, the feeder automation terminals FTUs in the circuit are successively disconnected according to the timing characteristic, and the operation is stopped until the feeder automation terminals FTUs detect all fault characteristic quantities, so that a plurality of stably-operating island micro-grids are formed.
The system of the invention is realized by adopting the following technical scheme: the utility model provides a little water and electricity island microgrid system of dividing after trouble, includes:
an upstream and downstream determination module: judging whether the line is located at the upstream or the downstream of a fault point according to fault characteristic information by a feeder automation terminal FTU of each line of the small hydropower island microgrid;
an island division module: through the upstream and downstream judgment module, when the judgment result is that the line is positioned at the downstream of the fault point, the line enters an island state, and island division is started;
disconnecting module of isolating switch: after the island division module is started, disconnecting each isolating switch at the downstream of the fault according to the magnitude of the power flow at the two sides before the fault according to the timing limit characteristic;
an island microgrid forming module: and the feeder automation terminals FTUs in the circuit are successively disconnected according to the timing characteristic, and the operation is stopped until all fault characteristic quantities are detected by the feeder automation terminals FTUs, so that a plurality of stably-operating island micro-networks are formed.
Compared with the prior art, the invention has the following advantages and beneficial effects:
1. according to the invention, by judging whether the line is positioned at the upstream and downstream positions of the fault point, when the line fault point is positioned at the downstream, the island division is started, and each isolating switch at the downstream of the fault is disconnected according to the magnitude of the power flow at the two sides before the fault according to the timing limit characteristic, so that the island microgrid with stable operation is formed, the fault recovery time is greatly reduced, and the unnecessary load loss is reduced.
2. According to the invention, the load flow before the fault recorded by the feeder automation terminal FTU is taken as an important basis for division, so that the complex load flow calculation after the fault is avoided, the calculation speed is increased, and the calculation resources are saved.
3. The island division can be completed only by using local fault information measured by the feeder automation terminal FTU, a specific communication channel does not need to be established, the construction cost is greatly saved, and the method is suitable for the backward foundation construction conditions of mountainous areas and rural areas with more distributed small hydropower micro-networks.
Drawings
FIG. 1 is a flow chart of the method of the present invention;
FIG. 2 is a schematic diagram of the invention based on the timing limit characteristic islanding of the power flow before the fault;
fig. 3 is a topological structure diagram of a small hydropower station island microgrid system of the invention;
fig. 4 is a per unit value of voltage of each node recorded by the feeder automation terminal FTU of the present invention.
Detailed Description
The present invention will be described in further detail with reference to examples and drawings, but the present invention is not limited thereto.
Examples
As shown in fig. 1, the method for dividing the microgrid of the post-fault small hydropower station island in the embodiment includes the following steps:
s1, after a fault occurs, judging whether the line is located at the upstream or the downstream of the fault point by a feeder automation terminal FTU of each line of the small hydropower island micro-grid according to fault characteristic information;
s2, if the feeder automation terminal FTU of each line of the small hydropower island microgrid judges that the line is located at the upstream of a fault point, the line cannot enter an island state, and island division is not started; if the line is located at the downstream of the fault point, the line enters an island state, island division is started, and the step S3 is entered;
s3, after the island division is started, disconnecting each isolating switch at the downstream of the fault according to the magnitude of the current at the two sides before the fault according to the timing characteristic;
and S4, the feeder automation terminals FTUs in the circuit are successively disconnected according to the timing characteristic, and the operation is stopped until the feeder automation terminals FTUs detect all fault characteristic quantities, so that a plurality of stably-operating island micro-grids are formed.
In this embodiment, the process of determining that the line is located upstream or downstream of the fault point in step S1 is as follows: according to the method, the line of the small hydropower island microgrid is a radiation line and is in open-loop operation under normal operation, and a feeder automation terminal FTU of each line of the small hydropower island microgrid can judge whether the line is located at the upstream or downstream of a fault point according to the direction of fault current in the line; if the fault current direction is pointed to the load by the bus, judging that the line is positioned at the upstream of the fault point; and if the fault current direction is from the load to the bus, judging that the line is positioned at the downstream of the fault point.
In this embodiment, the specific process after the island division is started in step S3 is as follows: after the island division is started, according to the magnitude of the power flow on the two sides of each line disconnecting switch recorded before the fault, each feeder automation terminal FTU located at the downstream of the fault point controls each disconnecting switch to be disconnected according to the timing limit characteristic shown in fig. 2, wherein the timing limit characteristic expression is as follows:
wherein the content of the first and second substances,t 0the value is set to 50ms for the minimum action delay; k is a positive time limit characteristic coefficient; i. j represents any two adjacent nodes in the small hydropower microgrid;
the effective value of the power flow between the node i and the node j is obtained; and t is the action delay of the feeder automation terminal FTU.
Specifically, in this embodiment, the smaller the power flow at both sides of each line disconnecting switch recorded before the fault is, the shorter the action delay of the disconnecting switch is; the larger the tide at two sides of each line disconnecting switch recorded before the fault is, the longer the action delay of the disconnecting switch is.
The present embodiment uses a small hydropower island microgrid system as shown in fig. 3 as an example; node voltage per unit values recorded by FTUs of feeder automation terminals of the small hydropower station island microgrid before the fault are shown in figure 4.
When a short-circuit fault occurs at a point f1 in the system, positive fault current is detected by feeder automation terminals FTUs located at nodes 1-8 and nodes 21-37, and the feeder automation terminal FTU judges that a line is located at the upstream of the fault point; and the feeder automation terminals FTU located at the nodes 9-19 and 39-51 detect reverse fault current, and the feeder automation terminals FTU judge that the line is located at the downstream of the fault point. Therefore, the feeder automation terminals FTUs of the nodes 1 to 8 and 21 to 37 located at the upstream of the fault point do not enter the islanding mode, and the feeder automation terminals FTUs of the nodes 9 to 19 and 39 to 51 located at the downstream of the fault point enter the islanding mode.
According to the flow numerical value recorded by the FTU shown in the figure 4, the flow between the node 13 and the node 14 before the fault is minimum, the isolating switch acts firstly according to the timing limit characteristic, and the nodes 14-19 are divided into islands 1; after the island 1 is formed, fault characteristic quantities cannot be detected by all feeder automation terminals (FTUs) in the island, and the island division mode is quitted. After the tidal current data of the nodes included in the island 1 are eliminated, the tidal current between the node 10 and the node 41 is minimum, so that the circuit between the two nodes is disconnected according to the timing limit characteristic, and the nodes 41-51 are divided into the island 2; after the island 2 is formed, fault characteristic quantities cannot be detected by FTUs of the feeder automation terminals of all nodes in the island 2, and the island division mode is quitted. Similarly, the nodes 11-13 and 38-40 can be divided into islands 3 and 4, respectively, according to the same principle. Finally, the line downstream of the fault point of the small hydropower island microgrid is divided into 4 island microgrids capable of stably operating, and the division result is shown in fig. 4.
Based on the same inventive concept, the invention also provides a micro-grid partitioning system for the small hydropower station isolated island after the fault, which comprises the following steps:
an upstream and downstream determination module: judging whether the line is located at the upstream or the downstream of a fault point according to fault characteristic information by a feeder automation terminal FTU of each line of the small hydropower island microgrid;
an island division module: through the upstream and downstream judgment module, when the judgment result is that the line is positioned at the downstream of the fault point, the line enters an island state, and island division is started;
disconnecting module of isolating switch: after the island division module is started, disconnecting each isolating switch at the downstream of the fault according to the magnitude of the power flow at the two sides before the fault according to the timing limit characteristic;
an island microgrid forming module: and the feeder automation terminals FTUs in the circuit are successively disconnected according to the timing characteristic, and the operation is stopped until all fault characteristic quantities are detected by the feeder automation terminals FTUs, so that a plurality of stably-operating island micro-networks are formed.
The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations, and simplifications are intended to be included in the scope of the present invention.
Claims (4)
1. A method for dividing a micro-grid of a small hydropower station island after a fault is characterized by comprising the following steps:
s1, after a fault occurs, judging whether the line is located at the upstream or the downstream of the fault point by a feeder automation terminal FTU of each line of the small hydropower island micro-grid according to fault characteristic information;
s2, if the feeder automation terminal FTU of each line of the small hydropower island microgrid judges that the line is located at the upstream of a fault point, the line cannot enter an island state, and island division is not started; if the line is located at the downstream of the fault point, the line enters an island state, island division is started, and the step S3 is entered;
s3, after the island division is started, disconnecting each isolating switch at the downstream of the fault according to the magnitude of the current at the two sides before the fault according to the timing characteristic;
and S4, the feeder automation terminals FTUs in the circuit are successively disconnected according to the timing characteristic, and the operation is stopped until the feeder automation terminals FTUs detect all fault characteristic quantities, so that a plurality of stably-operating island micro-grids are formed.
2. The method for dividing the microgrid of a post-fault small hydropower station island according to claim 1, wherein the process of judging whether the line is located at the upstream or downstream of the fault point in the step S1 is as follows: according to the method, a small hydropower station island microgrid circuit is a radiation-shaped circuit and is in open-loop operation under normal operation, and a feeder automation terminal FTU of each circuit of the small hydropower station island microgrid judges whether the circuit is located at the upstream or downstream of a fault point according to the direction of fault current in the circuit; if the fault current direction is pointed to the load by the bus, judging that the line is positioned at the upstream of the fault point; and if the fault current direction is from the load to the bus, judging that the line is positioned at the downstream of the fault point.
3. The method for dividing the microgrid of the post-fault small hydropower station island according to claim 1, wherein the specific process after the island division is started in the step S3 is as follows: after island division is started, according to the magnitude of the power flow on two sides of each line disconnecting switch recorded before the fault, each feeder automation terminal FTU located at the downstream of the fault point controls each disconnecting switch to be disconnected by using a timing characteristic, wherein the timing characteristic expression is as follows:
wherein, t0Minimum action delay; k is a positive time limit characteristic coefficient; i. j represents any two adjacent nodes in the small hydropower microgrid respectively;
the effective value of the power flow between the node i and the node j is obtained; and t is the action delay of the feeder automation terminal FTU.
4. The system for dividing the microgrid of a post-fault small hydropower station island according to claim 1, characterized by comprising:
an upstream and downstream determination module: judging whether the line is located at the upstream or the downstream of a fault point according to fault characteristic information by a feeder automation terminal FTU of each line of the small hydropower island microgrid;
an island division module: through the upstream and downstream judgment module, when the judgment result is that the line is positioned at the downstream of the fault point, the line enters an island state, and island division is started;
disconnecting module of isolating switch: after the island division module is started, disconnecting each isolating switch at the downstream of the fault according to the magnitude of the power flow at the two sides before the fault according to the timing limit characteristic;
an island microgrid forming module: and the feeder automation terminals FTUs in the circuit are successively disconnected according to the timing characteristic, and the operation is stopped until all fault characteristic quantities are detected by the feeder automation terminals FTUs, so that a plurality of stably-operating island micro-networks are formed.
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- 2021-09-27 CN CN202111133669.4A patent/CN113809742A/en active Pending
Patent Citations (4)
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|---|---|---|---|---|
| US20110115308A1 (en) * | 2008-07-21 | 2011-05-19 | Zhao Wang | Feeder automation system and method for operating the same |
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| CN102882197A (en) * | 2012-10-30 | 2013-01-16 | 山东电力集团公司烟台供电公司 | DG (distributed generation)-containing power distribution network distributed protection and control method |
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