A graph theory-based wide-area protection method for ship closed-loop power systems
Patent Information
- Application Number
- CN202610621220.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-05-08
- Publication Date
- 2026-09-04
AI Technical Summary
[0004]本发明针对船舶闭环电力系统双向多源潮流导致传统过流保护难以适应的问题，提供一种基于图论的船舶闭环电力系统广域保护方法，通过构建系统有向图模型、形成节点-边关联矩阵、边电流故障状态向量，进而完成故障定位计算，实现故障区域的快速、准确判定，满足保护选择性与速动性要求
本发明的有益效果在于：本发明基于图论的船舶闭环电力系统广域保护方法，无需预先整定复杂的保护配合级数，适应船舶闭环电力系统双向多回路潮流的动态变化；利用船舶电网各支路已有的电流互感器和集中式母排电压互感器信息获得各支路电流大小及方向信息，无需额外硬件，通信与计算负担小；可准确区分区内与区外故障，避免传统保护的方向性失配问题；满足选择性与速动性要求，同时为全局智能诊断与故障自愈提供拓扑信息基础。
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of relay protection technology for ship power systems, specifically relating to a graph theory-based wide-area protection method for ship closed-loop power systems, which is particularly suitable for high-end ship types such as marine engineering vessels and mobile platforms equipped with DP-2 / 3 level dynamic positioning systems. Background Technology
[0002] Shipboard closed-loop electrical systems, with their advantages of energy saving, high power supply reliability, and strong system survivability, are gradually replacing traditional radial topologies and becoming the mainstream power supply solution for high-level dynamically positioned ships. However, the closed-loop structure introduces a multi-source, multi-loop topology, causing fault currents to exhibit a complex flow pattern of bidirectional and multi-source superposition. Traditional three-stage overcurrent protection systems, designed based on unidirectional power flow and single-end power supply, are prone to maloperation or failure to operate in closed-loop systems, seriously threatening power grid safety.
[0003] While existing overcurrent protection based on directional elements can detect bidirectional currents, its settings are insufficient to accommodate different operating modes in scenarios involving frequent changes in ship operating conditions, large capacity of multiple generator units, and significant differences in power ratios. Graph theory has been applied in land-based ring network protection, but existing research mostly ignores the ring characteristics or decouples the ring network into a tree-like network, failing to directly apply it to the full-domain protection of ship closed-loop power systems. Therefore, there is an urgent need for a ship power grid relay protection method that can adapt to bidirectional power flow, quickly and accurately locate fault areas, and eliminate the need for complex settings. Summary of the Invention
[0004] This invention addresses the problem that traditional overcurrent protection is inadequate for bidirectional multi-source power flow in ship closed-loop power systems. It provides a graph theory-based wide-area protection method for ship closed-loop power systems. By constructing a directed graph model of the system, forming a node-edge association matrix and an edge current fault state vector, the method can complete fault location calculation, achieve rapid and accurate determination of the fault area, and meet the requirements of protection selectivity and speed.
[0005] The technical solution of this invention is: a wide-area protection method for a ship's closed-loop power system based on graph theory, comprising the following steps: Step S1: Construct a directed graph model of the ship's closed-loop power system, divide the protected equipment into several protection areas as nodes, and each area does not contain circuit breakers that can control the on / off state of the line; define the circuit breakers connecting each protection area as directed edges, and the direction of the directed edges is consistent with the reference direction of the current transformer at the corresponding circuit breaker. Step S2: Establish the node-edge association matrix of the directed graph model. M ( T ); Step S3: Monitor the current amplitude and direction at each circuit breaker in real time. When any one or more side currents exceed the set value, the fault judgment process is initiated to generate a side current fault state vector. L F (T), its elements l Fj The value is 1, -1, or 0 depending on the actual current over-limit state and direction. Step S4: Based on the node-edge association matrix M ( T ) and the edge current fault state vector L F (T) Calculate the fault location vector F ( T ), its elements f i The calculation formula is: in, i For node sequence number, j The edge number is... n Let be the total number of edges in the directed graph, and ∏ denote the chain multiplication operation; based on the fault location vector... F ( T Determine the fault area by analyzing the values of each element in the table. Step S5: Send a trip command to the circuit breaker associated with the faulty area to isolate the faulty area.
[0006] Furthermore, in step S1, each protection zone does not contain a circuit breaker that can control the switching on and off of the line; the same-name terminals of all current transformers are uniformly arranged on the end point or start point of the directed edge, forming a globally consistent symbol convention.
[0007] Furthermore, in step S2, a directed graph is provided. T Include m Each node and n The edge, the node-edge association matrix M ( T )for m × n An dimensional matrix, whose elements m ij The rules for determining the value are as follows: If node i With edge j If not connected, then m ij =0; If node i For the edge j The starting point, i.e., the node from which the edge current flows out in the reference direction. i ,but m ij =-1; If nodei For the edge j The endpoint, i.e., the side current reference direction flowing into the node. i ,but m ij =1.
[0008] Furthermore, in step S3, the preset protection start-up setting value is 1.3 to 3 times the rated value of the corresponding side current; the element l Fj The specific rules for determining the value are as follows: If the edge j If the current does not reach the preset protection start-up setting value, then l Fj =0; If the edge j If the current reaches the preset protection start-up setting value and the actual direction is consistent with the reference direction, then l Fj =1; If the edge j If the current reaches the preset protection start-up setting value and its actual direction is opposite to the reference direction, then... l Fj =-1.
[0009] Furthermore, in step S4, the rule for determining the fault area based on the values of each element in the fault location vector F(T) is as follows: like f i If ≥2, then the node is determined. i Fault occurred within the affected area; like f i =1, then determine the node i No fault current flowed through it; like f i =0, then determine the node i An out-of-area fault occurred.
[0010] Furthermore, the node i When an in-zone fault occurs, f i The value is equal to 2. k The power, where k For nodes i The number of valid edges in a connection; when k When =1, maintain f i The judgment result of ≥2 shall be executed according to the traditional single-end backup protection logic.
[0011] Furthermore, the plurality of protection areas include generator area, medium-voltage busbar area, bus tie cable area, medium-voltage load area and low-voltage busbar area, and can be extended to power grid structures of more voltage levels according to the division method of claim 1.
[0012] Furthermore, in step S3, each regional protection unit synchronizes its time using a unified clock source through the ship's local area network, encapsulates the local circuit breaker current amplitude and direction status into a message, and uploads it to the central protection decision unit. The central protection decision unit then concatenates the messages according to the directed edge numbering order to generate the edge current fault state vector. L F ( T ).
[0013] Furthermore, the method also includes a voltage-assisted blocking step: in generating the side current fault state vector L F ( T Before the fault occurs, the voltage amplitude of the corresponding busbar is collected. When the voltage amplitude is lower than a preset threshold of the rated voltage, fault state vector generation is initiated; otherwise, the corresponding fault state vector is... l Fj Forced to be set to 0 to block false starts caused by load fluctuations.
[0014] Furthermore, the method performs a polarity self-verification process before system commissioning: by injecting test current or comparing the power flow direction under normal operating conditions, it automatically verifies and corrects the reference direction symbol of the abnormal side, ensuring that the global symbol convention is consistent with the actual physical wiring. The beneficial effects of this invention are as follows: This invention provides a graph-based wide-area protection method for ship closed-loop power systems, eliminating the need for pre-setting complex protection coordination levels and adapting to the dynamic changes in bidirectional, multi-loop power flow within the ship's closed-loop power system; it utilizes existing current transformers and centralized busbar voltage transformers in each branch of the ship's power grid to obtain the magnitude and direction of current in each branch, requiring no additional hardware and reducing communication and computational burden; it can accurately distinguish between faults within and outside the protection zone, avoiding the directional mismatch problem of traditional protection; it meets the requirements of selectivity and speed, while providing a topological information basis for global intelligent diagnosis and fault self-healing. Attached Figure Description
[0015] Figure 1 This is a flowchart of the wide-area protection method for a ship's closed-loop power system according to the present invention.
[0016] Figure 2 A single-line diagram illustrating a typical structure of a ship's closed-loop electrical system; Figure 3 Example diagram of protection zone division for a ship's closed-loop electrical system; Figure 4 This is an example directed graph for a ship's closed-loop electrical system. Detailed Implementation
[0017] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.
[0018] like Figure 1 The flowchart shown is a wide-area protection method for a ship's closed-loop power system according to the present invention. The method specifically includes the following steps: 1) Construct a directed graph model of the ship's closed-loop power system: Divide the protected equipment into several protection zones, such as generators, medium-voltage busbars, bus tie cables, medium-voltage loads, and low-voltage busbars. Each zone is defined as a node; each zone does not contain circuit breakers that can control the on / off state of the lines. The circuit breakers connecting each zone are defined as directed edges, with the edge direction consistent with the reference direction of the current transformer at the circuit breaker. All current transformers with the same name are uniformly located at the end or start of the directed edge, forming a globally consistent symbol convention. Before system commissioning, a polarity self-check process is performed. By injecting test current or comparing with the normal operating power flow direction, the reference direction symbol of abnormal edges is automatically corrected to ensure that the global symbol convention is consistent with the actual physical wiring.
[0019] 2) Establish nodes Edge Incidence Matrix: Given a directed graph T Include m Each node and n Edge, definition m × n Node-Edge Incidence Matrix M ( T ), its elements m ij Values are determined according to the following rules: ①If node i With edge j If not connected, then m ij =0; ②If node i For the edge j The starting point (the node from which the edge current flows out in the reference direction), then m ij =-1; ③If node i For the edge j The endpoint (where the edge current flows into the node in the reference direction) then m ij =1.
[0020] 3) Obtaining the edge current fault state vector: Each regional protection unit synchronously samples via the ship's local area network using a unified clock source, packaging the local circuit breaker current amplitude and direction status into a message and uploading it to the central protection decision unit. Under short-circuit faults, the current amplitude increases significantly (reaching more than three times the rated value near the power source and also higher than the normal value at the far end). If the edge current amplitude is used as the starting criterion, the setting value can be 1.3 to 3 times the rated current. The current amplitude at each circuit breaker is monitored in real time. When any one or more edge currents exceed the setting value, the fault judgment process is initiated. The central unit concatenates the edge currents in sequence to generate a 1× n Step-edge current fault state vector L F (T), its elements l Fj Defined as: ①If the edge j If the current does not reach the set value, then l Fj =0; ②If the side j If the current reaches the set value and the actual direction is consistent with the reference direction, then l Fj =1; ③If the side j If the current reaches the set value and the actual direction is opposite to the reference direction, then l Fj =-1.
[0021] In generating the edge current fault state vector L F ( T Before the fault occurs, the voltage amplitude of the corresponding busbar is collected. When the voltage amplitude is lower than a preset threshold of the rated voltage, fault state vector generation is initiated; otherwise, the corresponding fault state vector is... l Fj Forced to be set to 0 to block false starts caused by load fluctuations.
[0022] 4) Calculate the fault location vector and determine the fault area: Define m ×1 order fault location vector F (T), its elements f i Calculate using the following formula: (1) In the formula: ∏ represents a series of multiplication operations. i For node sequence number, i =1,2,…, m ; j The edge number is... j =1,2,…, n .
[0023] The rules for determining the fault area are as follows: ①If f i If ≥2, then the node is determined. i Fault occurred within the affected area; ②If f i =1, then node i No fault current flowed through it; ③If f i =0, then node i An out-of-area fault occurred.
[0024] For multi-directional power flow nodes with k≥2 connected edges, this method can achieve highly selective fault location; for radial nodes with k=1, this method is still compatible and can be configured as a backup for traditional protection.
[0025] 5) Execute protection actions: based on the fault location vector F The output of (T) sends a trip command to the circuit breaker associated with the corresponding node (protection area) to isolate the fault area.
[0026] by Figure 2 Taking the ship's closed-loop integrated power system as an example, the system includes 3 generators, 3 sections of 6.6kV medium-voltage busbars, 3 distribution transformers, 1 medium-voltage frequency converter load, and 3 sections of 400V low-voltage busbars. According to... Figure 3 The area is divided into protection zones, which are connected by circuit breakers to form a system. Figure 4 The directed graph shown has 16 nodes and 18 edges: generator region (Z2, Z6, Z10), medium-voltage busbar region (Z1, Z5, Z9), bus tie cable region (Z4, Z8, Z12), medium-voltage load region (Z3, Z7, Z11, Z13), and low-voltage busbar region (Z14, Z15, Z16).
[0027] Establish the node-edge association matrix, as shown in Table 1. Select Z1 (medium-voltage busbar area), Z2 (generator area), Z3 (medium-voltage load area), Z4 (bus tie cable area), and Z14 (low-voltage busbar area) as fault points respectively. The edge current fault state vectors under different area faults are shown in Table 2. Substitute into formula (1) to calculate the fault location vector. The calculation results of the fault location vectors under different area faults are shown in Table 3. For example, when an intra-area fault occurs in the medium-voltage busbar area Z1, the results shown in the first column of Table 3 are as follows. f 1 = 16 ≥ 2 and the remaining nodes f i The value is 0 or 1, therefore the fault is determined to be in node Z1. Similarly, the faults in generator area Z2, medium-voltage load area Z3, bus tie cable area Z4, and low-voltage busbar area Z14 are simulated respectively, and all can be accurately determined.
[0028] Table 1
[0029] Table 2
[0030] Table 3
[0031] After the fault area is determined, the protection device sends a trip command to all circuit breakers associated with the fault area to completely isolate the fault.
[0032] The embodiments described above merely illustrate specific implementations of the present invention, and while the descriptions are detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.
Claims
1. A graph theory-based wide-area protection method for a ship's closed-loop power system, characterized in that, Includes the following steps: Step S1: Construct a directed graph model of the ship's closed-loop power system, and divide the protected equipment into several protection areas as nodes. Each area does not contain circuit breakers that can control the connection and disconnection of the line. The circuit breaker connecting each protection zone is defined as a directed edge, and the direction of the directed edge is consistent with the reference direction of the current transformer at the corresponding circuit breaker. Step S2: Establish the node-edge association matrix of the directed graph model. M ( T Step S3: Monitor the current amplitude and direction at each circuit breaker in real time. When any one or more side currents exceed the set value, the fault judgment process is initiated to generate a side current fault state vector. L F (T), its elements l Fj The value is 1, -1, or 0 based on the actual current over-limit state and direction; Step S4: Based on the node-edge association matrix... M ( T ) and the edge current fault state vector L F (T) Calculate the fault location vector F ( T ), its elements f i The calculation formula is: in, i For node sequence number, j The edge number is... n Let be the total number of edges in the directed graph, and ∏ denote the chain multiplication operation; based on the fault location vector... F ( T The numerical values of each element in the equation determine the fault area; Step S5: Send a trip command to the circuit breaker associated with the fault area to isolate the fault area.
2. The graph theory-based wide-area protection method for ship closed-loop power systems according to claim 1, characterized in that, In step S1, each protection zone does not contain a circuit breaker that can control the switching on and off of the line; the same-name terminals of all current transformers are uniformly arranged on the end or start side of the directed edge, forming a globally consistent symbol convention.
3. The graph theory-based wide-area protection method for ship closed-loop power systems according to claim 1, characterized in that, In step S2, a directed graph is provided. T Include m Each node and n The edge, the node-edge association matrix M ( T )for m × n An dimensional matrix, whose elements m ij The rule for determining the value is: if the node i With edge j If not connected, then m ij =0; if node i For the edge j The starting point, i.e., the node from which the edge current flows out in the reference direction. i ,but m ij =-1; If node i For the edge j The endpoint, i.e., the side current reference direction flowing into the node. i ,but m ij =1.
4. The graph theory-based wide-area protection method for ship closed-loop power systems according to claim 1, characterized in that, In step S3, the preset protection start-up setting value is 1.3 to 3 times the rated value of the corresponding side current; the element l Fj The specific rules for determining the value of edge are as follows: j If the current does not reach the preset protection start-up setting value, then l Fj =0; if the edge j If the current reaches the preset protection start-up setting value and the actual direction is consistent with the reference direction, then... l Fj =1; if the edge j If the current reaches the preset protection start-up setting value and the actual direction is opposite to the reference direction, then l Fj =-1.
5. The graph theory-based wide-area protection method for ship closed-loop power systems according to claim 1, characterized in that, In step S4, the rule for determining the fault area based on the values of each element in the fault location vector F(T) is as follows: If f i If ≥2, then the node is determined. i Fault occurred within the affected area; like f i =1, then determine the node i No fault current flowed through it; like f i =0, then determine the node i An out-of-area fault occurred.
6. The graph theory-based wide-area protection method for ship closed-loop power systems according to claim 5, characterized in that, The node i When an in-zone fault occurs, f i The value is equal to 2. k The power, where k For nodes i The number of valid edges in a connection; when k When =1, maintain f i The judgment result of ≥2 shall be executed according to the traditional single-end backup protection logic.
7. The graph theory-based wide-area protection method for ship closed-loop power systems according to claim 1, characterized in that, The protection zones include generator zones, medium-voltage busbar zones, bus tie cable zones, medium-voltage load zones, and low-voltage busbar zones, and can be extended to power grid structures of more voltage levels according to the division method of claim 1.
8. The graph theory-based wide-area protection method for ship closed-loop power systems according to claim 1, characterized in that, In step S3, each regional protection unit synchronizes its time using a unified clock source via the ship's local area network, encapsulates the local circuit breaker current amplitude and direction status into a message, and uploads it to the central protection decision unit. The central protection decision unit then concatenates the messages according to the directed edge numbering order to generate the edge current fault state vector. L F ( T ).
9. The graph theory-based wide-area protection method for ship closed-loop power systems according to claim 1, characterized in that, The method further includes a voltage-assisted blocking step: in generating the edge current fault state vector L F ( T Before the fault, the voltage amplitude of the corresponding busbar is collected. When the voltage amplitude is lower than a preset threshold of the rated voltage, the fault state vector generation is enabled; otherwise, the corresponding fault state vector is generated. l Fj Forced to be set to 0 to block false starts caused by load fluctuations.
10. The graph theory-based wide-area protection method for ship closed-loop power systems according to claim 1, characterized in that, The method performs a polarity self-verification process before the system is put into operation: by injecting test current or comparing the power flow direction under normal operating conditions, the reference direction symbol of the abnormal side is automatically verified and corrected to ensure that the global symbol convention is consistent with the actual physical wiring.