Radiation type loop-free power distribution network island generation method for power restoration by adopting SNOP (simple noise rejection operation)
Technical Field
The invention relates to a method for generating an isolated island of a radiation type loop-free power distribution network by adopting SNOP (single operational noise amplifier) for power restoration.
Background
The distribution network is an important part in terminal power supply, and with the wide integration of distributed energy, the defects of a fixed topological structure and a priority control method of the traditional distribution network are increasingly highlighted. Aiming at the problem, the application of a novel power electronic technology to improve the active regulation and control capability of the power distribution network becomes an important solution. Among them, a soft-open-Switch (SNOP), which is one of new power electronic devices, is a power electronic device installed at a conventional interconnection switch, has flexible voltage and power regulation capability and superior performance, and also has a significant optimization function in reducing network loss and improving voltage level, and thus has been paid attention by related researchers.
At present, SNOP application is mainly focused on node voltage optimization and power flow regulation and control in a conventional environment, and researchers carry out deep research on the aspects of configuration optimization, control and the like in the conventional environment, for example, the SNOP configuration optimization method in the conventional operating environment is established by comprehensively considering network loss and power system operation indexes; according to a double closed-loop control strategy, researchers propose a feeder flow control method of the SNOP under normal grid operation conditions. In addition, on the basis of analysis in the aspect of economic benefits, researchers consider both network loss optimization benefits and investment costs, and through analyzing the relation between the SNOP cost, loss reduction benefits and equipment capacity, an SNOP capacity and installation position planning scheme based on economic benefits is provided. Although the basic configuration and application of the SNOP in the power system can be realized by the above planning and optimizing configuration scheme, the net loss reduction yield of the SNOP rapidly tends to be saturated along with the increase of the SNOP capacity, so if the SNOP is only used for reducing the network loss of the power system under the conventional operating condition, the actual yield of the equipment is low, and the high investment cost becomes a main limiting factor of the multi-SNOP planning, which is not favorable for the popularization and application.
Considering that the SNOP has the capability of rapid power supply restoration, and meanwhile, a power system in the coastal region of southeast of China is easily damaged by natural weather disasters such as typhoon and the like, so that a large-scale power supply island is formed, if the SNOP is applied to realizing the post-disaster power supply restoration under extreme natural weather, the practical application benefit of the SNOP can be greatly improved.
Disclosure of Invention
Based on the above shortcomings, the invention aims to provide a radiation type loop-free power distribution network island generation method for power supply restoration by using SNOP, which can simply and quickly analyze island node combination information capable of restoring power supply by the SNOP after an electric power system has an island, provide basic data for SNOP profit analysis under extreme weather conditions, obtain all island node combinations in advance, facilitate power grid dispatching personnel to make timely optimization and adjustment according to the island node combinations and power grid state indexes when an actual natural disaster occurs, and further utilize the quick power restoration capability of the SNOP to avoid large-scale power failure accidents of the power distribution network.
The technical scheme of the invention is as follows: a radiation type loop-free power distribution network island generation method for power supply recovery by adopting SNOP (single operational noise) comprises the following steps:
the method comprises the following steps: forming complete topological connection between SNOP nodes, and classifying topology nodes of power distribution network containing SNOP
Firstly, defining an island: under the condition of not using SNOP, the node loses power supply; and (II) the node can recover power supply through SNOP, the set formed by the above nodes of the recoverable power supply island is called an island,
firstly, generating a topological structure of a power distribution network containing an SNOP (simple network operation protocol), wherein the topological structure needs to ensure that the SNOP can obtain required power from a balance node, dividing the topological structure into a direction I and a direction II according to the flow direction of active power flow passing through the SNOP, and classifying nodes in the power distribution network containing the SNOP according to positions and functions after generating a complete node topology of the power distribution network, wherein various nodes are specifically defined as follows:
(1) SNOP node: the method comprises the following steps that defined as an intermediate node for connecting a balance node and an SNOP, when a topological structure is formed, the SNOP node must meet the condition of complete connection between the SNOP and the balance node, so that the SNOP can acquire required power from the balance node;
(2) root node: defining a node for flowing SNOP active power;
(3) a terminal node: the terminal nodes comprise two types of nodes, and the first type of terminal nodes are end points of the power distribution network branches; the second type of terminal node is a final node connected with the SNOP along the active power flow direction of the SNOP;
(4) and (3) contact nodes: defining the node connected with more than 1 branch, and defining the root node or the contact column point at the same time;
(5) an island node: the island nodes are defined as nodes which can be connected with the root node but not directly connected with the balance node, the island nodes can be simultaneously defined as contact nodes or terminal nodes, the SNOP node combinations of the two types of tidal currents flowing downwards are different, and the corresponding island node combinations are also different;
step two: island node gradual retrieval according to topological structure
Taking the root node as an initial node, and counting the island nodes point by point from the initial node until a terminal node or a contact node appears; when the nodes are searched to contact nodes, the island nodes on the node branch are searched one by one and merged into an island until the next contact node or terminal node appears;
step three: repeating iterative retrieval algorithm to generate all SNOP-containing power distribution network isolated islands
Completing island node retrieval under a single contact node or a terminal node according to the process in the step two; and if the un-searched island nodes exist, repeating the step two until all the island nodes are searched, only terminal nodes appear, completing island generation in two SNOP active power flow directions, and counting all island combinations generated in the algorithm flow.
The invention has the following advantages and beneficial effects:
(1) the algorithm makes full use of the radial topological characteristic of the power distribution network, performs topology analysis and node definition according to the tidal current direction and the position of the SNOP equipment in the topological structure of the power distribution network, reduces the difficulty of overall system analysis, and provides a topological analysis means for a power system basically comprising the SNOP equipment for researchers.
(2) The SNOP island algorithm is generated according to the network topology, is simple and practical, and has high calculation efficiency. The algorithm can be realized in modes of manual analysis or computer programming and the like no matter a large-scale power distribution system or a miniature power system is highly practical, and research and analysis of contents such as SNOP equipment income and the like under the condition of extreme natural disasters are facilitated for researchers. Meanwhile, in combination with the risk conditions such as line breakage and the like, the data result can provide data support for installation and pre-planning of the SNOP equipment.
(3) All the island node combinations can be obtained in advance through the algorithm, power grid dispatching personnel can make timely optimization and adjustment according to the island node combinations and power grid state indexes when actual natural disasters occur, and large-scale power failure accidents of the power distribution network are avoided by means of the quick power restoration capacity of the SNOP equipment.
Drawings
FIG. 1 is an exemplary diagram of a simple power distribution system topology including SNOP;
FIG. 2 is a flow chart of the steps of the present patent;
fig. 3 is a schematic diagram of an island generation embodiment process.
Detailed Description
The invention will be further illustrated by way of example with reference to the accompanying drawings.
Example 1:
the invention relates to a power system fault state analysis technology under natural weather disasters, in particular to an algorithm technology for generating an island node combination which can be recovered by SNOP equipment to supply power in a system island by analyzing a power system topological structure applied by the SNOP equipment under the natural weather disasters such as typhoons, and the following is introduced in detail:
as shown in fig. 1-2, a method for generating an island of a radial loop-free power distribution network by using SNOP for power restoration includes the following steps:
the method comprises the following steps: and forming complete topological connection among the SNOP nodes, and classifying the topological nodes of the power distribution network containing the SNOP.
Firstly, defining an island: the island node capable of recovering power supply under the SNOP action provided in the design has the following two preconditions: firstly, under the condition of not using the SNOP, the node loses power supply; and secondly, the node can recover power supply again through the SNOP equipment, and a set formed by the nodes of the recoverable power supply island is called an island.
In the step, a power distribution network topological structure containing the SNOP equipment is generated firstly, the SNOP equipment needs to be ensured to obtain required power from a balance node in the topological structure, and the topological structure is divided into a direction I and a direction II according to the flow direction of active power flow passing through the SNOP. After generating a complete distribution network node topology, classifying nodes in the distribution network containing the SNOP according to positions and functions, wherein various nodes are specifically defined as follows:
(1) SNOP node: defined as the intermediate node where the balancing node is connected to the SNOP device. Example node [0-1-18-19-20-21] in FIG. 1 (a). When the topology is formed, the SNOP node must satisfy the condition of complete connection between the SNOP device and the balancing node, thereby ensuring that the SNOP device can obtain the required power from the balancing node.
(2) Root node: defined as the node from which the active power of the SNOP device flows out. Fig. 1(a) corresponds to node number 11, and fig. 1(b) corresponds to node number 21.
(3) A terminal node: the terminal nodes comprise two types of nodes, and the first type of terminal nodes are end points of the power distribution network branches; the second type of terminal node is the final node connected to the SNOP in the SNOP active power flow direction. For example, nodes 17, 32, 24 in direction I may be defined as terminal nodes of the first type and node number 18 in direction II as terminal nodes of the second type.
(4) And (3) contact nodes: defined as nodes connected to more than 1 branch. The root node may also act as a contact list point at the same time. For example, in the direction I, nodes 11, 5 and 2 are all contact nodes, where node 11 can be defined as a root node and a contact node at the same time; while no contact nodes are present in direction II.
(5) An island node: an island node is defined as a node that may be connected to a root node but not directly to a balancing node. An island node may be defined as a contact node or a terminal node at the same time. For example, for the direction I, taking node number 9 as an example, when a disconnection occurs, the node may be connected to node number 11 (root node) through node number 10, but not directly connected to the balanced node (node number 0), so that the node may be defined as an island node. The SNOP node combinations of the two types of power flows flowing downwards are different, and the corresponding island node combinations are also different.
Through the definition of each node in the power distribution network topology structure, the island node in the nodes can be analyzed to be the node capable of quickly recovering power supply through SNOP after the extreme natural disaster occurs, and then the island node is searched according to two directions in the first step.
Step two: and gradually searching the island nodes according to the topological structure.
Taking a root node as an initial node, and counting island nodes point by point from the initial node until a terminal node or a contact node appears; and when the nodes are searched to contact nodes, the island nodes on the node branch are searched one by one and merged into an island until the next contact node or terminal node appears.
Step three: and repeating the iterative retrieval algorithm to generate all the SNOP-containing power distribution network islands.
Completing island node retrieval under a single contact node or a terminal node according to the process in the step two; and if the un-searched island nodes exist, repeating the step two until all the island nodes are searched, and only terminal nodes appear. And completing the island generation in two SNOP active power flow directions, and counting all island combinations generated in the algorithm flow.
Example 2
According to the topological structure of the 33-node power distribution network containing the SNOP in the figure 1(a), example analysis is carried out, and all possible island combinations are solved by adopting the design algorithm. Wherein each type of node and the included nodes are shown in table 1.
Table 1 distribution network topology node classification
According to the classification condition of each node in table 1, an island which may exist is generated according to the design search algorithm, and a specific island generation process demonstration is shown in fig. 3. The generation process is described later with reference to fig. 3.
And selecting a node 11 (root node) according to the node classification as a starting point of a retrieval algorithm, wherein the node 11 divides the island into a left part and a right part integrally, the left part island node combination positioned in front of the contact node can be a combination of [11-10], [11-10-9] to [11-10- … -5] and the like, and the right part island node can be similar to the left part island node and can comprise a combination of [11-12], [11-12-13] to [11-12- … -17] and the like. When the retrieval algorithm reaches the contact node, the non-SNOP nodes with branch parts connected with the island nodes are merged into the corresponding islands, such as the branch No. 5-25- … -32 connected with the node No. 5 or the branch No. 5-4-3- … -24, and the corresponding branch island node combinations are shown in FIG. 3. In addition, due to the existence of the contact nodes, new islands can be formed by arbitrarily combining the generated island parts, for example, the islands [9-10- … -15] can be formed by islands [11-10-9] and [11-12- … -15] on two sides of the node 11, wherein each generated combination comprises the node 11 (root node) to realize the connection with the SNOP equipment.
Repeating the algorithm program until only 24 and 32 terminal nodes appear, completing the algorithm iteration process, forming all island combinations shown in figure 3, and obtaining 325 types of island combinations which are consistent with the direction I through combination and arrangement.
By way of example, it is clear that a search for all possible island combinations can be easily implemented according to the present design algorithm. According to different island node combinations and the occurrence probability thereof, researchers and dispatching departments can obtain the basic composition of the SNOP recoverable power supply island node in the extreme disaster situation. The method is beneficial to researchers to further research the SNOP configuration and application method so as to improve the SNOP income, thereby meeting the requirements of popularization of high-cost SNOP and optimization of a power distribution network system. And the whole algorithm process is simple and clear, easy to realize and has strong engineering practical value. The method has strong practicability for a large-scale power distribution system or a micro power system, and is beneficial to research and analysis of contents such as SNOP equipment income under the condition of extreme natural disasters by researchers. Meanwhile, if the risk conditions such as line breakage and the like are combined, the data result can provide data support for installation and pre-planning of the SNOP equipment. All the island node combinations can be obtained in advance through the algorithm, power grid dispatching personnel can make timely optimization and adjustment according to the island node combinations and power grid state indexes when actual natural disasters occur, and large-scale power failure accidents of the power distribution network are avoided by means of the quick power restoration capacity of the SNOP equipment.