Mountainous area micro-grid monitoring data return method based on chained unmanned aerial vehicle group cache relay communication

Abstract

The invention relates to the technical field of micro-grid wireless communication, and discloses a mountainous area micro-grid monitoring data return method based on chained unmanned aerial vehicle group cache relay communication, which comprises the following steps of: 1, constructing a mountainous area micro-grid ground monitoring station into a tree topology architecture by adopting a hierarchical clustering method, each node generates monitoring data to be transmitted at regular time, and has data caching and wireless communication capabilities; and step 2, carrying out inter-node link data relay transmission by adopting the chained unmanned aerial vehicle group carrying the cache, wherein the unmanned aerial vehicle configured by each node link moves back and forth along the link. Compared with the prior art, the system has the advantages that the networking technology and the unmanned aerial vehicle group cache and relay communication technology are adopted to transmit mass monitoring data of the micro-grid in the remote mountainous area, so that the transmission and communication cost of the mass monitoring data of the micro-grid in the remote area is greatly reduced; the flexibility of monitoring the micro-grid in the remote area is enhanced, and the monitoring cost is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of microgrid wireless communication, and specifically refers to a method for transmitting monitoring data of a mountain microgrid based on chained UAV swarm caching relay communication. Background Technique

[0002] In recent years, with the rapid development of various communication technologies, the digitization of the power system has been significantly improved. However, under the current power system, the requirements for communication capabilities in services such as power consumption information collection, demand response, new energy power generation, and intelligent inspection are also constantly increasing, bringing new challenges to the development of China's smart grid. A microgrid is a small-scale, local power supply system, usually composed of renewable energy sources (such as solar energy, wind energy) and energy storage devices, and can operate independently of the main grid. The microgrid has the ability of intelligent management and dispatching, and can provide stable and reliable power for a specific area when the power supply is unstable or interrupted. Compared with the conventional power grid: (1) The microgrid has a smaller scale, usually composed of small-capacity distributed energy sources, energy storage devices, loads, and energy management systems; (2) It has higher flexibility and autonomy, can achieve local energy self-sufficiency, and even operate independently of the main grid when necessary; (3) Reliable power supply, the use of distributed energy sources increases the reliability and resilience of power supply, especially in emergency situations such as natural disasters, power supply can be quickly restored; (4) Small environmental impact, the microgrid tends to use clean and renewable energy sources, with less impact on the environment. (5) High technical requirements: The microgrid requires more advanced control technologies and intelligent devices to effectively manage distributed energy sources. In summary, the microgrid is an important direction for the development of the power system towards intelligence and greenness, but it also faces problems and challenges such as high technical requirements and more complex systems.

[0003] Mountain microgrids can utilize the rich mountain green energy (light, wind, water, etc.) to generate electricity. Currently, the main problems existing in mountain power grids are weak grid structures, single-line and single-transformer power supplies, high line failure rates, voltage fluctuations caused by small hydropower, etc. Compared with the power quality problems of traditional power grids, the power quality problems in microgrids are more prominent due to the use of a large number of distributed energy sources and power electronic devices, thus posing a more severe test for mountain microgrids.

[0004] In order to monitor the status of mountain microgrids and ensure their normal operation, it is necessary to equip mountain microgrids with a necessary communication network to transmit real-time monitoring data back, including data collected by multi-mode sensors such as video, voice, pictures, etc. However, there are the following two main problems in the communication of mountain microgrids: First, the power business in mountainous areas is increasing continuously, but the communication system is backward, fiber optic communication cannot cover, and the inspection methods of power lines and equipment are backward, which cannot meet the communication requirements of the multi-dimensional services of microgrids, affecting the power supply company's timely grasp of the operation of mountain microgrids; Second, the communication reliability is low. Since the construction cost of wireless private networks in remote mountainous areas is relatively high, it reduces the application prospect of wireless private networks in remote mountainous areas and cannot effectively realize the information interaction of mountain microgrids.

[0005] With the development of UAV technology, using UAV swarms to perform inspection, monitoring, communication relay and other operations in complex and harsh environments has become a low-cost and high-benefit solution. Nowadays, there are already some communication technologies based on UAV caching technology. However, by utilizing the high mobility and flexibility of chain UAVs and working in cooperation by carrying caching devices, it is possible to transmit important monitoring data back to a long distance to a remote monitoring and control center, evaluate the potential risks of power grid equipment, and ensure the efficient operation and maintenance of microgrids. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to overcome the above technical difficulties and provide a method for transmitting monitoring data of mountain microgrids based on chain UAV swarm caching relay communication; to solve the problem of transmitting a large amount of monitoring data of microgrids in remote mountainous areas. This method can well meet the monitoring problem of the equipment status of microgrids in remote mountainous areas by the remote control center.

[0007] To solve the above technical problem, the technical solution provided by the present invention is as follows:

[0008] A method for transmitting monitoring data of mountain microgrids based on chain UAV swarm caching relay communication, including the following steps:

[0009] Step 1: Use the hierarchical clustering method to construct the ground monitoring stations of mountain microgrids into a tree-like topological structure. Each node regularly generates monitoring data to be transmitted and has the ability to cache data and wireless communication.

[0010] Step 2: Use chain UAV swarms carrying caches to perform data relay transmission between nodes. The UAVs configured for each node link move back and forth along this link.

[0011] Step 3: Calculate the monitoring data generation rate and relay transmission rate of each UAV transmission link, and make the relay transmission rate higher than the generation rate by reasonably adjusting the UAV flight interval.

[0012] Further, the specific process of step 1 is as follows:

[0013] The microgrid monitoring station is located in a remote area and cannot directly conduct broadband communication and data transmission with the remote monitoring and control center. The hierarchical clustering algorithm is used to construct a tree-like topological structure for the microgrid monitoring station and a single communication base station. The leaf nodes are the monitoring stations in the remote area, and the root node is the communication base station, which can transmit data to the remote monitoring center through the communication network; the monitoring data is transmitted between the root node and its child nodes by wired optical cable; each node has an effective communication range, has the ability to cache data and perform wireless transmission, and periodically generates monitoring data to be transmitted. The monitoring data can only be saved in the local cache of the monitoring station until the drone hovers within its effective communication range and sends / transmits the monitoring data to the drone through a wireless link; each node aggregates the monitoring files generated and forwarded by the child nodes derived from this node and transmits them to the parent node of this node; after multi-hop relay transmission, the drone aggregates the monitoring data to the root node with better communication conditions, and the root node transmits the monitoring data back to the remote microgrid monitoring center through the optical fiber via the base station.

[0014] Further, the specific process of step 2 is as follows:

[0015] Direct communication between different monitoring station nodes is not possible, and a rotor drone with a cache is used for data transmission; both the drone and the monitoring station are equipped with wireless communication transceiver devices and caches. The cache capacity and energy of the monitoring station are unlimited, while the drone has limited cache capacity and energy. The wireless transmission rate is limited by the distance between the drone and the monitoring station, noise, and interference from other hovering drones; the drone flies uniformly along a straight line between two monitoring nodes when flying between different monitoring nodes, and hovers when storing / forwarding monitoring data within the effective communication range of the source / destination node. The node link distance is much greater than the effective communication distance of the node; the energy consumption of the drone includes round-trip movement energy consumption, hovering energy consumption, and wireless communication energy consumption; each monitoring station node can provide a charging service for the drone. When the drone reaches within the effective communication range of the monitoring station node, if the remaining energy is not enough to support its flight to the next node, it stops at this monitoring node for charging after completing the current data transmission, and the monitoring station node releases a fully charged drone without cached data to replace this drone.

[0016] Further, the specific process of step 3 is as follows:

[0017] The drone swarm configured for each node link moves back and forth along that link. The drones configured for each node link communicate with the node using the same frequency band, while different node links use different frequency bands to communicate with the node. When multiple drones belonging to the same node link communicate with the monitoring node simultaneously, they are evenly distributed on a circular hovering trajectory. The hovering heights of drones belonging to different node links are different. For each monitoring node transmission link, multiple drones are used to transmit data in a chained manner. If each drone fills up / transmits the buffer space, it immediately flies in the opposite direction to another node of the drone link. Calculate the monitoring data generation rate and relay transmission rate of each drone transmission link, and through reasonable allocation of the drone flight interval, make it satisfy that the relay transmission rate is higher than the generation rate. Repeat the above steps until the relay transmission rates of all node links are higher than the monitoring data generation rate.

[0018] The advantages of the present invention compared with the prior art are as follows:

[0019] The present invention uses networking technology, drone swarm caching, and relay communication technology to transmit a large amount of monitoring data of remote mountain microgrids, greatly reducing the cost of transmitting and communicating a large amount of monitoring data of remote microgrids, enhancing the flexibility of monitoring remote microgrids, and reducing the monitoring cost. Description of the Drawings

[0020] Figure 1 is a flowchart of the present invention.

[0021] Figure 2 is a schematic diagram of the wireless transmission rate of the chained drone swarm in the same node of the present invention. Detailed Embodiment

[0022] The following further elaborates on the present invention in conjunction with the embodiments and the drawings of the specification.

[0023] The ground monitoring nodes of the microgrid collect a large amount of video monitoring data. This type of data is large in volume and has relatively low requirements for transmission real-time. In the mountainous environment, the distance between two ground monitoring nodes is far, the environment between the monitoring stations is relatively complex, with a large number of obstacles, trees, mountains, etc. distributed, and there are no public communication devices such as base stations in the vicinity. Therefore, it is difficult to transmit a large amount of video files back to the control center using traditional wireless communication methods. In response to this, a method for transmitting monitoring data of mountain microgrids back based on chained drone swarm caching and relay communication is proposed, specifically as follows:

[0024] 1. Construct the ground monitoring stations of the mountain microgrid into a tree-like topological structure

[0025] Such as Figure 1As shown in the figure, there are several ground monitoring stations distributed in the mountain microgrid. Each monitoring station can provide charging services for the unmanned aerial vehicles (UAVs), and is equipped with wireless communication and caching devices, with an effective communication distance of R. The distance between monitoring stations is much greater than the effective communication distance of the monitoring stations, and direct communication between any two monitoring stations is not possible. Abstracting a single communication base station and monitoring stations as nodes, setting a maximum node distance threshold, and using the agglomerative hierarchical clustering algorithm to construct them into an M-level tree-like topological structure. Among them, the first-level leaf nodes are the monitoring stations in remote areas, the M-level root node is the communication base station, and each level of nodes has child nodes and parent nodes. The communication base station root node communicates with its child nodes through optical fibers. Each monitoring station node will regularly generate monitoring data, including: video, voice, images, etc. Each child node will aggregate the monitoring data generated by itself and all its child nodes, and transmit it to the parent node of this node via a swarm of UAVs. After multi-hop relay transmission, the UAVs will aggregate the monitoring data to the (M - 1)-level node with better communication conditions, which will transmit it to the communication base station root node through optical fibers, and the monitoring data will be backhauled to the remote microgrid monitoring center via the communication network.

[0026] 2. Relay transmission of link data between nodes based on a chain of UAVs with caches

[0027] Ultra-long-distance video transmission is achieved in the microgrid monitoring through networking relay technology. Each ground monitoring station in the microgrid is regarded as a node, and the connection lines between different nodes are regarded as edges. UAVs are distributed in the entire microgrid ad hoc network, and collect or backhaul data for each node in the ad hoc network of microgrid monitoring stations, and travel back and forth along the edges in the ad hoc network.

[0028] Set the coordinates of the nth monitoring node s in the mth level of the microgrid topological structure as p m,n = [x m,n , y m,n , z m,n m,n T , assuming there are a total of N c UAVs simultaneously performing wireless data transmission with the monitoring node. The hovering height of all UAVs is H, and they are evenly distributed on a circular trajectory centered on the monitoring node with an effective communication radius of R, and each UAV has a line-of-sight communication link with the monitoring node. When the kth UAV hovers above the monitoring node, its position can be expressed as where the phase variable φ k = 2πk / N c , 1 ≤ k ≤ N c . According to Shannon's theorem, when there are N c UAVs communicating simultaneously, the data transmission rate of the line-of-sight wireless link from a single UAV to the ground monitoring station node can be calculated as:

[0029]

[0030] Wherein, B is the system transmission bandwidth; For the existence of N c Under the condition of UAV communication, UAV k is connected to monitoring node s m,n The signal-to-interference-to-noise ratio of a line-of-sight link can be expressed as:

[0031]

[0032] in, is the power of Gaussian white noise; P com represents the signal transmission power, β is the path loss attenuation factor, Represents the relationship between drone k and monitoring node s m,n The distance between Indicates that at monitoring node s m,n The distance between UAV k and UAV k' within the communication range. The calculation formula is:

[0033]

[0034] The symbol ||·|| represents the modulo operation. Similarly, The calculation formula is:

[0035]

[0036] From the above, we can see that the transmission rate of UAV k is not only related to the distance and noise between monitoring stations, but also to the number of UAVs communicating simultaneously within the range of the current monitoring node.

[0037] Next, the total transmission rate of the wireless link between the chained drone swarm and the monitoring node will be calculated.

[0038] For monitoring nodes s m,n In terms of the monitoring data generation rate It can be calculated as:

[0039]

[0040] Among them, T c is the time duration for generating monitoring data; S m,n Represents node s m,n In duration T c The size of the monitoring data file generated within S m-1,n' Indicates that the n'th monitoring node in the (m-1)th level is in the time length T c The size of the monitoring data file generated within; N m Represents node s m,n The number of child nodes contained.

[0041] The time interval between any two drones in the chain - type drone swarm is the same, denoted as ΔT, and ΔT < T c , and it has an integer - multiple relationship with T c The number N of hovering drones that communicate with node s m,n simultaneously can be calculated according to the following formula: c

[0042]

[0043] where N c is the smallest positive integer that satisfies the above formula; S UAV represents the cache storage space size carried by a single drone. The variable R in the above formula m,n omits the drone variable because the distances between multiple drones and the monitoring station and other drones are exactly the same. So it calculates the wireless transmission rate of any one drone in the scenario where p drones communicate with the monitoring - station node simultaneously. To solve this problem, the method of incrementally trying values can be used to obtain the value of N c , that is: where is the maximum value of the number of drones that communicate with a single monitoring node simultaneously.

[0044] As Figure 2 shown, within the entire time duration T c range, the total size S of the monitoring data files transmitted by all drones within the range of node s m,n can be calculated as: F

[0045]

[0046] Then the average wireless transmission rate of this node link can be calculated as:

[0047]

[0048] To ensure that the monitoring data can be transmitted back to the remote monitoring center in time, each node transmission link should satisfy that the average transmission rate is higher than the generation rate, that is, satisfy the following rate - constraint relationship:

[0049]

[0050] For this constraint, the numerical method is used to solve the optimal time interval ΔT of the chain - type drone swarm. Construct the objective index The initial value of the time interval is where is node s m,n ​​When there is only one drone within the range, the transmission rate is judged to see if it meets the rate transmission constraint condition of formula (11). If it meets, stop the iteration and output the time interval ΔT; otherwise, ΔT l+1 = ΔT l + δT, where δT represents the single-step increase step size of the time interval, and the subscript l represents the l-th step. Calculate the change rate of the target index ΔF = F l+1 - F l ; Repeat the above steps until the change rate of the target index ΔF is less than the specified threshold ε, that is, ||ΔF|| < ε. Finally, the optimal time interval ΔT of the chain-type drone swarm can be solved.

[0051] 3. For the energy consumption of the drone's motion state

[0052] The energy consumption of the drone mainly includes two parts: motion energy consumption and communication energy consumption. In communication energy consumption, the drone transmits / receives signals at a fixed power P com ; The motion energy consumption includes propulsion energy consumption and hovering energy consumption. When the rotor drone moves forward at a constant speed V, the formula for calculating its total motion power consumption is as follows:

[0053]

[0054] Among them, P0 and P i respectively represent the blade profile power and induction power in the hovering state; U tip represents the tip speed of the rotor blade; v0 represents the average rotor induction speed in hovering; ρ and A represent the air density and the rotor disk area; d0 and s respectively represent the fuselage drag ratio and the rotor firmness. When the drone is in the hovering state, its power can be calculated as:

[0055] P hov = P(V)| V＝0 = P0 + P i (13)

[0056] Then the energy consumption required for a single drone to hover within the effective communication range of the node is:

[0057] E hov = P hov [(N c - 1)ΔT + ΔT x (14)

[0058] The energy consumption required for communication during hovering is:

[0059] E com = P com [(N c - 1)ΔT + ΔT x (15)

[0060] Set the distance between two monitoring nodes as D, and this distance is much greater than the effective communication distance of the monitoring station node, i.e., D >> R. Then the energy consumption required for a single flight is as follows:

[0061] E rout = P(V)D / V (16)

[0062] The total energy of the battery carried by a single drone is E S , and the current remaining energy is E exi . To ensure that the drone can return to any monitoring node before the battery runs out, the following constraint relationship should hold:

[0063] E S - E exi ≥α(E hov + E com ) + E rout (17)

[0064] where α ∈ {0, 1} is a binary variable. When its value is 0, it means the drone cache stores monitoring data; when its value is 1, it also means the drone cache stores monitoring data.

[0065] The above elaborates in detail on any node link in the microgrid tree - shaped topological structure network. Repeating the above steps for each node link in the microgrid tree - shaped topological network can achieve the back - transmission of a large amount of monitoring data of the microgrid in remote mountainous areas.

[0066] The above describes the present invention and its implementation manners, and this description is not restrictive. If those of ordinary skill in the art are inspired by it and, without departing from the gist of the present invention, design similar embodiments to this technical solution without creative efforts, they shall fall within the protection scope of the present invention.

Claims

1. A method for transmitting monitoring data of a microgrid in a mountainous area based on chained drone group cache relay communication, characterized in that: The following steps are involved: Step 1: Use the hierarchical clustering method to construct the mountain microgrid ground monitoring station into a tree topology architecture. Each node generates monitoring data to be transmitted regularly and has the ability to cache data and wireless communication; Step 2: A chained drone group carrying a cache is used to relay data between nodes. The drones configured for each node link move back and forth along the link. Step 3: Calculate the monitoring data generation rate and relay transmission rate of each UAV transmission link, and reasonably adjust the UAV flight interval to ensure that the relay transmission rate is higher than the generation rate.

2. According to claim 1, a method for transmitting monitoring data of a mountain microgrid based on chained drone group cache relay communication is characterized in that: The specific process of step 1 is as follows: The microgrid monitoring station is located in a remote area and cannot directly communicate and transmit data via broadband with the remote monitoring and control center. A hierarchical clustering algorithm is used to construct the microgrid monitoring station and a single communication base station into a tree topology architecture, in which the leaf nodes are monitoring stations in remote areas and the root node is a communication base station, which can transmit data with the remote monitoring center through the communication network; wired optical cables are used to transmit monitoring data between the root node and its child nodes; each node has an effective communication range, the ability to cache data and transmit wirelessly, and regularly generates monitoring data to be transmitted. The monitoring data can only be saved in the local cache of the monitoring station until the drone hovers within its effective communication range and sends / returns the monitoring data to the drone through a wireless link; each node aggregates the monitoring files generated and forwarded by the child nodes derived from the node, and transmits them to the parent node of the node; after multi-hop relay transmission, the drone aggregates the monitoring data to the root node with better communication conditions, and the root node transmits the monitoring data back to the remote microgrid monitoring center via the base station through optical fiber.

3. According to claim 1, a method for transmitting monitoring data of a mountain microgrid based on chained drone group cache relay communication is characterized in that: The specific process of step 2 is: Different monitoring station nodes cannot communicate directly with each other, so a rotorcraft drone with cache is used for data transmission. Both the drone and the monitoring station are equipped with wireless communication transceivers and cache. The cache capacity and energy of the monitoring station are unlimited, while the cache capacity and energy of the drone are limited. The wireless transmission rate is limited by the distance between the drone and the monitoring station, noise, and interference from other hovering drones. When the UAV flies between different monitoring nodes, it flies at a constant speed along the straight line between the two monitoring nodes. It adopts a hovering state when storing / forwarding monitoring data within the effective communication range of the source / destination node. The node link spacing is much larger than the effective communication distance of the node. The energy consumption of the UAV includes the energy consumption of round-trip motion, hovering energy consumption, and wireless communication energy consumption. Each monitoring station node can provide charging services for the UAV. When the UAV reaches the effective communication range of the monitoring station node, if the remaining energy is not enough to support its flight to the next node, it will stop at the monitoring node for charging after completing the current data transmission, and the monitoring station node releases a full-energy, non-cached UAV to replace the UAV.

4. According to claim 1, a method for transmitting monitoring data of a mountain microgrid based on chained drone group cache relay communication is characterized in that: The specific process of step 3 is as follows: The drone swarm configured for each node link moves back and forth along the link. The drones configured for each node link communicate with the node at the same frequency, and different node links communicate with the nodes at different frequencies. When there are multiple drones belonging to the same node link communicating with the monitoring node at the same time, they are evenly distributed on the circular hovering trajectory. The hovering heights of drones belonging to different node links are different. For each monitoring node transmission link, multiple drones are used to transmit data in a chained manner. If each drone has full / completed the cache space, it will immediately fly in the opposite direction to another node of the drone link. The monitoring data generation rate and relay transmission rate of each drone transmission link are calculated, and the drone flight interval is reasonably adjusted to ensure that the relay transmission rate is higher than the generation rate. Repeat the above steps until the relay transmission rates of all node links are higher than the monitoring data generation rate.

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