A Method for Reliable Transmission of Smart Grid Data

Abstract

The present invention relates to the field of communication technologies, and particularly relates to a method for reliable transmission of smart grid data, including constructing a space-air-ground integrated smart grid system, which includes multiple nodes. Each node periodically broadcasts data packets, and each node updates its own neighbor list according to the data packets broadcast by all nodes; when the source node receives an electric power service, if the electric power service is a protected service, a multi-path selection method is used to determine the routing path of the electric power service, and if the electric power service is an unprotected service, a routing algorithm based on greedy forwarding is used to determine the routing path of the electric power service; the present invention can ensure the reliable transmission of data and prevent data loss.

Description

Technical Field

[0001] The present invention relates to the field of communication technologies, and particularly to a method for reliable transmission of smart grid data. Background Art

[0002] In recent years, with the vigorous development of wireless communication technologies such as big data and artificial intelligence, the power industry is evolving towards a smart grid based on the physical power grid. A smart grid integrates technologies such as information communication, sensing measurement, and automation with power grid infrastructure, and is a new type of clean, friendly, safe, and efficient power grid with a certain level of automation and high self-healing ability, mainly responsible for the reliable transmission of information such as measurement, regulation, control, protection, and dispatching during the power production process. In the power communication network of a smart grid, the dispatching center station combines grid status information with regular information interaction of the subordinate stations, conducts comprehensive analysis and makes corresponding decisions, including issuing dispatching, protection, and control commands to each communication sub-station or terminal station, thereby achieving the intelligent dispatching and management of the power grid. However, to achieve the goals of intelligent management and real-time dispatching of the power grid, a large number of information collection devices must be installed in the five major links of power generation, transmission, transformation, distribution, and power consumption in the smart grid, which will inevitably generate a large amount of data in the smart grid, and the data volume increases exponentially. In addition, various service data will be generated during the operation of the power grid. Therefore, for a smart grid that highly depends on functions such as dispatching, protection, control, and monitoring of the communication system, designing an efficient and reliable routing algorithm is of great significance for ensuring the extremely stable operation of end-to-end service transmission.

[0003] In addition, communication network failures are inevitable. When the power services carried by the smart grid are interrupted after being damaged by human or natural disasters, it is necessary to design an efficient re-routing algorithm according to its differentiated performance index requirements to ensure the continuous transmission of services. Protection switching before a communication network failure and dynamic recovery after a failure are two common fault handling methods and are also the keys to realizing reliable service transmission. Hardware enhancement and reliable dual-routing algorithm design are two important protection implementation technologies. An efficient and reliable dual-routing algorithm can achieve rapid service recovery by switching between primary and backup routes without changing the structure of the existing network topology, ensure service performance, and reduce network operation and maintenance costs. Therefore, to meet the latency-sensitive requirements and reliability requirements of different power services and ensure rapid system fault handling, the present invention proposes a dual-routing algorithm and a routing recovery method based on service priority. Summary of the Invention

[0004] To solve the above problems, the present invention provides a method for reliable transmission of smart grid data, including the following steps:

[0005] S1. Construct an integrated space-air-ground intelligent power grid system, which includes multiple nodes. Each node broadcasts data packets regularly, and each node updates its own neighbor list according to the data packets broadcast by all nodes. The node types include satellite nodes and ground nodes;

[0006] S2. When the source node receives an electric power service, if the electric power service is a protected service, then execute step S3; if the electric power service is an unprotected service, then execute step S4;

[0007] S3. Use a multi-path selection method to determine the routing path of the electric power service;

[0008] S4. Use a routing algorithm based on greedy forwarding to determine the routing path of the electric power service.

[0009] Furthermore, the integrated space-air-ground intelligent power grid system includes a satellite network and an intelligent power grid. The satellite network includes multiple satellite nodes, and the intelligent power grid includes multiple ground nodes. The direct communication link between any two satellite nodes is called an ISL link, the direct communication link between any two ground nodes is called an ITL link, and the direct communication link between a satellite node and a ground node is called a TSL link. Each satellite node is provided with 5 ports, and 1 of the ports is used to connect to a ground node, and the remaining 4 ports are used to connect to neighbor satellite nodes.

[0010] Furthermore, the integrated space-air-ground intelligent power grid system also includes a node risk model and a communication delay model, where:

[0011] The node risk coefficient model is expressed as:

[0012]

[0013] where, represents the risk coefficient of node j; represents the number of failures of node j within the time period T;

[0014] The communication delay model includes:

[0015] ISL link queuing delay:

[0016]

[0017] where, represents the ISL link queuing delay from satellite node m to satellite node n, represents the number of data packets received by the port of satellite node m used to connect to satellite node n at the current moment t, represents the number of data packets sent by the port of satellite node m used to connect to satellite node n at the current moment t; P mnDenotes the average value of the total number of received and transmitted data packets from time t - Δ to time t at the port of satellite node m for connecting to satellite node n. Denotes the link capacity of the ISL link between satellite node m and satellite node n; Δ denotes the routing update period.

[0018] TSL link queuing delay:

[0019]

[0020] Among them, Denotes the TSL link queuing delay between satellite node m and ground node r. Denotes the number of data packets received at the port of satellite node m for connecting to ground node r at the current time t. Denotes the number of data packets sent at the port of satellite node m for connecting to ground node r at the current time t; P mr Denotes the average value of the total number of received and transmitted data packets from time t - Δ to the current time t at the port of satellite node m for connecting to ground node r. Denotes the link capacity of the TSL link between satellite node m and ground node r.

[0021] ISL link propagation delay:

[0022]

[0023] Among them, Denotes the ISL link propagation delay between satellite node m and satellite node n, d mn Denotes the distance between satellite node m and satellite node n, C denotes the wireless transmission speed.

[0024] TSL link propagation delay:

[0025]

[0026] Among them, Denotes the TSL link propagation delay between satellite node m and ground node r, d mr Denotes the distance between satellite node m and ground node r, C denotes the wireless transmission speed.

[0027] ISL link communication delay:

[0028]

[0029] Among them, Denotes the ISL link communication delay from satellite node m to satellite node n.

[0030] Further, step S3 uses a dual-routing path selection method to determine the routing path of the power service, including:

[0031] S31. Determine the destination node of the power service, and execute step S32 with the source node as the current node;

[0032] S32. The current node calculates the risk coefficient of each node in its neighbor list and sorts them in ascending order according to the risk coefficient; records the direct communication links between the current node and each node in its neighbor list, and calculates the link communication delay between the current node and each node in its neighbor list; calculates the selection coefficient between the current node and each node in its neighbor list through the risk coefficient and the link communication delay;

[0033] S33. Take each node in the neighbor list as the current node and return to step S32 until reaching the destination node and then enter step S34;

[0034] S34. Combine all direct communication links to obtain multiple combined routing paths from the source node to the destination node, calculate the total selection coefficient of each combined routing path, and sort all combined routing paths in ascending order according to the total selection coefficient to obtain a selection list;

[0035] S35. Take the first combined routing path in the selection list as the primary routing path and the second combined routing path as the backup routing path.

[0036] Further, step S4 uses a routing algorithm based on greedy forwarding for the routing path of the power service, including:

[0037] S41. Determine the destination node of the power service, and execute step S42 with the source node as the current node;

[0038] S42. Obtain the farthest distance between the current node and its neighbor nodes according to the neighbor list of the current node, and judge whether the number of neighbor nodes satisfying the farthest distance is greater than 1. If so, enter step S43; if not, select the neighbor node for forwarding, and then execute step S44;

[0039] S43. Judge whether there is a neighbor node of the type of ground node. If so, select a neighbor node of the type of ground node for forwarding, and then execute step S44; if not, randomly select a neighbor node for forwarding, and then execute step S44;

[0040] S44. Judge whether the selected neighbor node is the destination node. If so, end the loop to obtain the routing path of the power service; if not, take the neighbor node as the current node and return to step S42.

[0041] Further, when a fault occurs during the data transmission of an unprotected service through a routing path, find and determine the faulty section and non-faulty section of the routing path, and adopt a service restoration routing algorithm for link reselection for the faulty section, specifically including:

[0042] S51. Determine the fault source node and fault destination node in the faulty section; count all the candidate sections from the fault source node to the fault destination node in the system except for the faulty section, and form a candidate set;

[0043] S52. Traverse each candidate section in the candidate set, and kick out the candidate sections that do not meet the three constraints from the candidate set;

[0044] S53. Calculate the bandwidth availability of each candidate section in the candidate set, and select the candidate section corresponding to the maximum bandwidth availability for transmission.

[0045] Further, the three constraints include:

[0046] Flow conservation constraint:

[0047] Among them, represents the incoming traffic volume of the i-th node of the q-th candidate section of the power service k, represents the outgoing traffic volume of the i-th node of the q-th candidate section of the power service k; Sum kq represents the number of nodes on the q-th candidate section of the power service k;

[0048] Bandwidth constraint:

[0049]

[0050] Among them, L k,q represents the q-th reselection routing path of the power service k, and this reselection routing path is composed of the non-faulty section of the original routing path of the power service k and the q-th candidate section; represents the link from the i-th node to the j-th node in the q-th reselection routing path of the power service k, represents the required bandwidth for the power service k to transmit on the link ; represents the link The minimum available bandwidth;

[0051] Communication delay constraint:

[0052]

[0053] Among them, T(L k,q ) represents the communication delay of the q-th reselection routing path of the power service k, Denote the communication delay of the non-faulty section of the original routing path of power service k. Denote the communication delay of the q-th candidate section of power service k, and φ denotes the service communication delay threshold.

[0054] Furthermore, the calculation formula for bandwidth availability is:

[0055]

[0056] Wherein, Denote the bandwidth availability of the q-th candidate section. Denote the idle bandwidth of the q-th candidate section. Denote the total bandwidth of the q-th candidate section.

[0057] Advantages of the present invention:

[0058] The present invention sets different service types for smart grid services, and can better formulate different communication methods for services with different communication requirements to ensure the secure and reliable transmission of data.

[0059] The present invention designs a dual-path routing method and simultaneously sets a re-routing mechanism, which can ensure the reliable transmission of data and prevent data loss. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] Figure 1 Schematic diagram of the application scenario of the smart grid in the embodiment of the present invention;

[0061] Figure 2 Flowchart of the method of the present invention;

[0062] Figure 3 Schematic diagram of the network topology structure of the space-air-ground integrated smart grid system of the present invention;

[0063] Figure 4 Schematic diagram of the restored routing in the embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0064] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0065] As Figure 1As shown, the smart grid bears the key business transmissions that ensure power production and the informatization of power enterprises, such as relay protection, security and stability devices, dispatching automation, etc. Different types of services have different requirements for indicators such as communication latency, reliability, and security. According to the service type, power services can be divided into protected and unprotected services, as shown in Table 1.

[0066] Table 1 Power Service Types

[0067]

[0068] Among them, protected services are the key services in power production. Since they directly act on the power system, they mainly include relay protection services, security and stability control services, dispatching telephones, etc. The specific index requirements for their reliability, real-time performance, and security are shown in Table 2.

[0069] Table 2: Typical Power Services and Performance Parameters

[0070]

[0071] Based on the above service type division, the present invention provides a method for reliable transmission of smart grid data, as Figure 2 shown, including the following steps:

[0072] S1. Construct a space-air-ground integrated smart grid system, which includes multiple nodes. Each node regularly broadcasts data packets, and each node updates its own neighbor list according to the data packets broadcast by all nodes; the node types include satellite nodes and ground nodes.

[0073] Specifically, the present invention constructs a space-air-ground integrated smart grid system for the smart grid, which is composed of two parts: a satellite network and a smart grid. The satellite network consists of multiple low-earth orbit satellites, and each low-earth orbit satellite is regarded as a satellite node. The smart grid is an automated interactive network system composed of a communication network layer and a power system layer. The communication network layer mainly refers to the ground wide-area network, including grid terminals, power generation stations, switches, etc.; the power system layer is composed of power production units, intelligent electronic devices, and power consumption users; all of these are regarded as ground nodes, and the smart grid includes multiple ground nodes.

[0074] Due to the large scale and service differentiation of the smart grid, it is necessary to construct a network topology structure to ensure the reliable transmission of grid data; for this reason, the present invention refers to the direct communication link between any two satellite nodes as an ISL link, the direct communication link between any two ground nodes as an ITL link, and the direct communication link between a satellite node and a ground node as a TSL link; thus, the communication of the space-air-ground integrated smart grid system is abstracted as an undirected graph, as Figure 3As shown. In addition, there are 5 ports at each satellite node, with 1 port used to connect to the ground node and the remaining 4 ports used to connect to neighboring satellite nodes.

[0075] Specifically, the air-space-ground integrated intelligent power grid system further includes a node risk model and a communication delay model, where:

[0076] The node risk is considered in view of the impact caused by node failures. In the existing communication system, due to factors such as old equipment, discontinued equipment models, and termination of after-sales services, the reliability is reduced and the risk is increased. At the same time, factors such as manufacturing defects and human sabotage also exacerbate the risk. Therefore, in the present invention, according to the historical node failure data, the node risk coefficient is calculated through statistics.

[0077] The node risk coefficient model is expressed as:

[0078]

[0079] Among them, represents the risk coefficient of node j; represents the number of failures of node j within the time period T.

[0080] Considering the high reliability of communication network transmission, other QoS performance indicators such as service packet loss rate and bit error rate are not considered. According to queuing theory, the end-to-end service communication delay includes queuing delay, processing delay, and propagation delay. Since the processing delay is related to the performance of hardware devices, and the data is only transmitted between nodes and does not participate in data processing, the processing delay can be ignored. Since the air-space-ground integrated intelligent power grid system includes three types of links, the communication delay model includes:

[0081] ISL link queuing delay:

[0082]

[0083] Among them, represents the ISL link queuing delay from satellite node m to satellite node n, represents the number of data packets received by the port of satellite node m used to connect to satellite node n at the current time t, represents the number of data packets sent by the port of satellite node m used to connect to satellite node n at the current time t; P mn represents the average value of the total number of received and sent data packets by the port of satellite node m used to connect to satellite node n from time t - Δ to time t, represents the link capacity of the ISL link between satellite node m and satellite node n; Δ represents the routing update period;

[0084] TSL link queuing delay:

[0085]

[0086] Among them, represents the queuing delay of the TSL link from satellite node m to ground node r, represents the number of data packets received at the port of satellite node m used to connect to ground node r at the current time t, represents the number of data packets sent from the port of satellite node m used to connect to ground node r at the current time t; P mr represents the average value of the total number of data packets received and sent from the port of satellite node m used to connect to ground node r from time t - Δ to the current time t, represents the link capacity of the TSL link between satellite node m and ground node r;

[0087] The queuing delay of the ITL link is calculated in a conventional manner.

[0088] Propagation delay of the ISL link:

[0089]

[0090] Among them, represents the propagation delay of the ISL link between satellite node m and satellite node n, d mn represents the distance between satellite node m and satellite node n, and C represents the wireless transmission speed;

[0091] Propagation delay of the TSL link:

[0092]

[0093] Among them, represents the propagation delay of the TSL link between satellite node m and ground node r, d mr represents the distance between satellite node m and ground node r, and C represents the wireless transmission speed;

[0094] Propagation delay of the ITL link:

[0095]

[0096] Among them, represents the propagation delay of the TSL link between ground node o and ground node r, d or represents the distance between ground node o and ground node r, and C represents the wireless transmission speed;

[0097] Communication delay of the ISL link:

[0098]

[0099] Among them, Denote the communication delay of the ISL link from satellite node m to satellite node n.

[0100] Communication delay of the TSL link:

[0101]

[0102] Among them, Denote the communication delay of the TSL link from satellite node m to ground node r.

[0103] Communication delay of the ITL link:

[0104]

[0105] Among them, Denote the communication delay of the TSL link from ground node o to ground node r, Denote the queuing delay of the ITL link from ground node o to ground node r.

[0106] S2. When the source node receives an electric power service, if the electric power service is a protected service, then execute step S3; if the electric power service is an unprotected service, then execute step S4.

[0107] S3. Use the multi-path selection method to determine the routing path of the electric power service.

[0108] Specifically, step S3 uses the dual-routing path selection method to determine the routing path of the electric power service, including:

[0109] S31. Determine the destination node of the electric power service, and execute step S32 with the source node as the current node;

[0110] S32. The current node calculates the risk coefficient of each node in its neighbor list, and arranges them in ascending order according to the risk coefficient; record the direct communication link between the current node and each node in its neighbor list, and calculate the link communication delay between the current node and each node in its neighbor list; calculate the selection coefficient between the current node and each node in its neighbor list through the risk coefficient and the link communication delay, expressed as:

[0111]

[0112] Among them, α and β are weight coefficients, and α + β = 1, t ij Denote the link communication delay between the current node i and its neighbor node j, choice i,j Denote the selection coefficient between the current node i and its neighbor node j;

[0113] S33. Take each node in the neighbor list as the current node and return to step S32 until the destination node is reached, then enter step S34;

[0114] S34. Combine all direct communication links to obtain multiple combined routing paths from the source node to the destination node, calculate the total selection coefficient of each combined routing path, and sort all combined routing paths in ascending order of the total selection coefficient to obtain a selection list;

[0115] S35. Take the first combined routing path in the selection list as the primary routing path and the second combined routing path as the backup routing path.

[0116] In particular, the smart grid is an ultra-large-scale wireless communication network, and the data propagation delay through the ground network is greater than that through satellites. To efficiently and reliably transmit protected data, when the dual-routing path selection method is adopted in the present invention, it is considered from the ground to the satellite and then back to the ground.

[0117] S4. Use a routing algorithm based on greedy forwarding to determine the routing path of the power service.

[0118] Specifically, since the satellite node resources are limited and the satellite-ground delay is much higher than the ground-ground node delay, for unprotected service data, ground nodes are preferentially selected as data forwarding relay nodes to minimize the end-to-end delay. Step S4 uses a routing algorithm based on greedy forwarding for the routing path of the power service, including: S41. Determine the destination node of the power service, and take the source node as the current node to execute step S42;

[0119] S42. To minimize the number of hops, that is, to minimize the delay, if the farthest distance is selected for each hop, then the number of hops can be guaranteed to be the smallest. Therefore, obtain the farthest distance between the current node and its neighbor nodes according to the neighbor list of the current node, and judge whether the number of neighbor nodes satisfying the farthest distance is greater than 1. If so, enter step S43; if not, select the neighbor node for forwarding, and then execute step S44;

[0120] S43. Judge whether there is a neighbor node of the type of ground node. If so, select a neighbor node of the type of ground node for forwarding, and then execute step S44; if not, randomly select a neighbor node for forwarding, and then execute step S44;

[0121] S44. Judge whether the selected neighbor node is the destination node. If so, end the loop to obtain the routing path of the power service; if not, take the neighbor node as the current node, and return to step S42.

[0122] Specifically, communication network failures are inevitable. As the coupling degree between the physical power grid and the communication network gradually deepens, service transmission interruptions may trigger cascading failures in the power system. Therefore, it is very important to achieve rapid restoration of differentiated power services and confirm load balancing after a communication network failure. In the scenario of communication link failures, based on different service characteristics, the present invention proposes a routing restoration method for load balancing. For protected service types, in order to avoid excessive communication delays caused by re-routing, while ensuring service performance, the primary-backup routing switching method is generally adopted to ensure continuous service transmission when a failure occurs; for unprotected service types, when a link failure occurs, a service restoration routing algorithm is enabled.

[0123] Specifically, when a failure occurs during the data transmission of an unprotected service through a routing path, the faulty section and the non-faulty section of the routing path are found and determined, and the service restoration routing algorithm is used for link re-selection for the faulty section, specifically including:

[0124] S51. Determine the source node and destination node of the faulty section in the faulty section; count all the candidate sections from the source node to the destination node in the system except the faulty section, and form a candidate set;

[0125] S52. Traverse each candidate section in the candidate set, and kick out the candidate sections that do not meet the three constraints from the candidate set;

[0126] Specifically, the three constraints include:

[0127] Flow conservation constraint: The incoming traffic volume at each node in the candidate section is equal to the outgoing traffic volume, which is expressed as follows

[0128]

[0129] Among them, represents the incoming traffic volume of the i-th node of the q-th candidate section of power service k, represents the outgoing traffic volume of the i-th node of the q-th candidate section of power service k, Sum kq represents the number of nodes of the q-th candidate section of power service k;

[0130] Bandwidth constraint:

[0131]

[0132] Among them, L k,q represents the q-th reselected routing path of power service k, and this reselected routing path is composed of the non-faulty section of the original routing path of power service k and the q-th candidate section; represents the link from the i-th node to the j-th node in the q-th reselected routing path of power service k, Indicates the required bandwidth for power service k on the link during transmission, and represents the minimum available bandwidth of the link ;

[0133] Communication delay constraint:

[0134]

[0135] Among them, T(L k,q ) represents the communication delay of the q-th reselected routing path of power service k, represents the communication delay of the non-faulty section of the original routing path of power service k, represents the communication delay of the q-th candidate section of power service k, and represents the service communication delay threshold.

[0136] S53. Calculate the bandwidth availability of each candidate section in the candidate set, and select the candidate section corresponding to the maximum bandwidth availability for transmission.

[0137] Specifically, the calculation formula for bandwidth availability is:

[0138]

[0139] Among them, represents the bandwidth availability of the q-th candidate section, represents the idle bandwidth of the q-th candidate section, and represents the total bandwidth of the q-th candidate section.

[0140] In one embodiment, taking Figure 4 as an example, each circle represents a node, and the two numbers on each side respectively represent the available capacity and total capacity of the link between the two connected nodes. When a fault occurs in section 3-6 during the data transmission of the unprotected service through the routing path 1-3-6-8, in order to achieve service restoration and avoid the problem of network load imbalance caused by service convergence, the service restoration routing algorithm is enabled. First, determine the fault source node (i.e., Figure 4 node 3 in) and the fault destination node (i.e., Figure 4 node 6 in) in the faulty section; count all the candidate sections from the fault source node to the fault destination node in the system except the faulty section, including candidate section P1: 3-2-5-6, candidate section P1: 3-5-6, candidate section P1: 3-7-6; perform three constraint judgments on the three candidate sections. Assuming that all three candidate sections meet the communication index requirements such as delay and bandwidth of the service, calculate the bandwidth availability rates of the three sections to be 0.1255, 0.2054, and 0.1118 respectively. Therefore, the service is finally switched to path P2 for transmission.

[0141] In the present invention, unless otherwise clearly stipulated and defined, terms such as "installation", "setting", "connection", "fixation", "rotation" shall be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or integrated; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the communication inside two elements or the interaction relationship between two elements. Unless otherwise clearly defined, for those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0142] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for reliable transmission of smart grid data, characterized in that, It includes the following steps: S1. Construct an integrated space-air-ground intelligent power grid system, which includes multiple nodes. Each node broadcasts data packets regularly, and each node updates its own neighbor list according to the data packets broadcast by all nodes; the node types include satellite nodes and ground nodes; S2. When the source node receives an electric power service, if the electric power service is a protected service, then execute step S3; if the electric power service is an unprotected service, then execute step S4; S3. Determine the routing path of the electric power service by using a multi-path selection method, including: S31. Determine the destination node of the electric power service, and execute step S32 with the source node as the current node; S32. The current node calculates the risk coefficient of each node in its own neighbor list, and arranges them in ascending order according to the risk coefficient; record the direct communication link between the current node and each node in its neighbor list, and calculate the link communication delay between the current node and each node in its neighbor list; calculate the selection coefficient between the current node and each node in its neighbor list through the risk coefficient and the link communication delay; S33. Take each node in the neighbor list as the current node and return to step S32 until reaching the destination node and then enter step S34; S34. Combine all direct communication links to obtain multiple combined routing paths from the source node to the destination node, calculate the sum of the selection coefficients of each combined routing path, and arrange all combined routing paths in ascending order according to the sum of the selection coefficients to obtain a selection list; S35. Take the first combined routing path in the selection list as the main routing path, and the second combined routing path as the backup routing path; S4. Determine the routing path of the electric power service by using a routing algorithm based on greedy forwarding, including: S41. Determine the destination node of the electric power service, and execute step S42 with the source node as the current node; S42. Obtain the farthest distance between the current node and its neighbor nodes according to the neighbor list of the current node, and judge whether the number of neighbor nodes satisfying the farthest distance is greater than 1. If so, then enter step S43; if not, then select the neighbor node for forwarding, and then execute step S44; S43. Judge whether there is a neighbor node of the ground node type. If so, then select a neighbor node of the ground node type for forwarding, and then execute step S44; if not, then randomly select a neighbor node for forwarding, and then execute step S44; S44. Judge whether the selected neighbor node is the destination node. If so, then end the loop to obtain the routing path of the electric power service; if not, then take the neighbor node as the current node, and return to step S42.

2. The reliable data transmission method for smart grid according to claim 1, characterized in that, The described space-air-ground integrated smart grid system includes a satellite network and a smart grid. The satellite network includes multiple satellite nodes, and the smart grid includes multiple ground nodes. A direct communication link between any two satellite nodes is called an ISL link, a direct communication link between any two ground nodes is called an ITL link, and a direct communication link between a satellite node and a ground node is called a TSL link. Each satellite node is provided with 5 ports, and 1 of the ports is used to connect to a ground node, and the remaining 4 ports are used to connect to neighbor satellite nodes.

3. The reliable data transmission method for smart grid according to claim 2, wherein The space-air-ground integrated smart grid system further includes a node risk coefficient model and a communication delay model, where: The node risk coefficient model is expressed as: Among them, represents the risk coefficient of node j; represents the number of failures of node j within the time period T; The communication delay model includes: ISL link queuing delay: Among them, denotes the queuing delay of the ISL link from satellite node m to satellite node n, denotes the number of data packets received at the port used by satellite node m to connect to satellite node n at the current moment t, denotes the number of data packets sent from the port used by satellite node m to connect to satellite node n at the current moment t; P mn denotes the average value of the total number of data packets received and sent from the port used by satellite node m to connect to satellite node n from time t - Δ to time t, denotes the link capacity of the ISL link between satellite node m and satellite node n; Δ denotes the routing update period; TSL link queuing delay: Among them, represents the queuing delay of the TSL link between satellite node m and ground node r, represents the number of data packets received at the port of satellite node m used to connect to ground node r at the current moment t, represents the number of data packets sent from the port of satellite node m used to connect to ground node r at the current moment t; P mr represents the average value of the total number of data packets received and sent from the port of satellite node m used to connect to ground node r from time t - Δ to the current moment t, represents the link capacity of the TSL link between satellite node m and ground node r; ISL link propagation delay: Among them, represents the propagation delay of the ISL link between satellite node m and satellite node n, and d mn represents the distance between satellite node m and satellite node n, and C represents the wireless transmission speed; TSL link propagation delay: Among them, represents the propagation delay of the TSL link between satellite node m and ground node r, and d mr represents the distance between satellite node m and ground node r, and C represents the wireless transmission speed; ISL link communication delay: Among them, represents the communication delay of the ISL link from satellite node m to satellite node n.

4. The reliable transmission method of smart grid data according to claim 1, wherein When a fault occurs during the data transmission of unprotected services through a routing path, find and determine the faulty section and the non-faulty section of the routing path, and use a service restoration routing algorithm to reselect the link for the faulty section, specifically including: S51. Determine the faulty source node and the faulty destination node in the faulty section; count all the remaining candidate sections from the faulty source node to the faulty destination node in the system except the faulty section, and form a candidate set. S52. Traverse each candidate section in the candidate set, and kick out the candidate sections that do not meet the three constraints from the candidate set. S53. Calculate the bandwidth availability of each candidate section in the candidate set, and select the candidate section corresponding to the maximum bandwidth availability for transmission.

5. A reliable data transmission method for an intelligent power grid according to claim 4, characterized in that, The three constraints include: Flow conservation constraint: Among them, represents the incoming traffic volume of the i-th node of the q-th candidate section of power service k, represents the outgoing traffic volume of the i-th node of the q-th candidate section of power service k; Sum kq represents the number of nodes on the q-th candidate section of power service k; Bandwidth constraint: Among them, L k,q represents the q-th reselection routing path of power service k, which is composed of the non-faulty sections of the original routing path of power service k and the q-th candidate section; represents the link from the i-th node to the j-th node in the q-th reselection routing path of power service k, represents the power service k on the link the required bandwidth for transmission, represents the link the minimum available bandwidth; Communication delay constraint: where, T(L k,q ) represents the communication delay of the q-th reselection routing path of power service k, represents the communication delay of the non-faulty section of the original routing path of power service k, represents the communication delay of the q-th candidate section of power service k, represents the service communication delay threshold.

6. The reliable transmission method for smart grid data according to claim 4, characterized in that The calculation formula for bandwidth availability is: Among them, represents the bandwidth availability of the q-th candidate road section, represents the idle bandwidth of the q-th candidate road section, represents the total bandwidth of the q-th candidate road section.

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