Research On Static And Dynamic Networking Of Measurement Equipment Considering Time-varying Of Low Voltage Power Line Channel

With the continuous innovation and breakthrough of new energy technology,intelligent technology and other technologies,the power energy transmission and distribution links around the world are beginning to develop toward the smart grid.In the construction of advanced measurement system,which is an important part of smart grid construction,the demand-side measurement equipments of distribution network as one of the most important terminal products,the accurate and efficient acquisition of its information is the precondition for the construction and normal operation of advanced measurement system.With the vigorous promotion of intelligent application of the demand-side measurement equipments in distribution network and the construction and development of the advanced metering infrastructure,as the main means of information exchange between measurement equipments and advanced metering infrastructure,low-voltage power line communication undertakes the normal operation of information collection of measurement equipment and bidirectional real-time communication with AMI,therefore,ensuring the stability and reliability of its communication is of great significance to the construction and development of high-level measurement system in smart grid.According to the research of references,the research on improving the communication technology of low-voltage power line could be divided into two aspects:one is to improve the communication distance by studying the low-voltage power line channel(For example,the study of power line channel model,the study of noise suppression methods,etc.);the other is to use networking technology(For example,the method of relay routing)to increase the communication distance and improve the stability of the system.In the current range of communication distance of power line channel,this paper studies the networking technology of acquisition equipment which could not communicate at long distance.In the research process of low-voltage power line networking technology,in order to follow-up low-voltage power line networking modeling and simulation experiment smoothly,through the extensive application and development of smart meters in recent years,this paper takes smart meters as the main acquisition equipment of distribution network side,carries out relevant experimental research on networking technology.The main research work is outlined as follows:1.Establishment of communication path for nodes of low voltage power line.By researching the cobweb method proposed in the literature,it is found that there are signal conflicts caused by multiple relays simultaneously communicating with the same node in the communication path for nodes.In order to improve the efficiency of networking and reduce signal conflict,this paper studies the method of layered relay selection,and through the construction of communication path for nodes,it is found that in the process of building low-voltage power line communication path for nodes,smart meters belonging to the same layer of subnet do not communicate with each other,thus greatly reducing the establishment time of communication path for nodes,improving efficiency and reducing a large number of signal conflict problem.2.The load time-varying model of low-voltage power line channel is established.In the experiment of collecting information on the measuring device(such as smart meter)by the concentrator,it is found that there will be some abnormal information that could not be collected or the information collected may be abnormal at some moments.After research,it is mainly due to the random access of load,that is,the low-voltage power line channel has load time-varying in the process of communication.In order to study the impact of random access of load on power line channel communication,this paper establishes a load time-varying model of the low-voltage power line channel,and provides a basis for the establishment of the objective function in the subsequent low-voltage power line network.3.A static and dynamic combination networking method for low voltage power line is proposed.The specific method process is as follows:Firstly,based on the established the communicable path of each node of the low-voltage power line,for the case where multiple relay nodes communicate with the same node at the same time,this paper first selects the optimal communication path by static networking method.That is,when the initial networking is performed by the static networking method,the link index is established by considering the communication quality and the number of relay forwarding,and it is used as the objective function for finding the optimal relay.In order to find out the optimal upper level relay automatically,this paper adopts the ant colony algorithm,and improves it by setting the direction function and constructing a new heuristic information function.Through MATLAB simulation experiments,it is found that the optimal communication branch can be quickly selected for communication.In practice,the concentrator will always communicate with the remote smart meters according to the selected path.Then,when there is information abnormality in the process of communication,this paper uses the dynamic networking method to re-route the abnormal path.The link index established at this time needs to consider the time-varying of power line channel on the basis of considering both communication quality and relay forwarding number.In this paper,by analyzing the changes of the user's power consumption at each collection time,the key parameters of the link index are dynamically adjusted.Finally,the improved ant colony algorithm is used to re-route the abnormal branches.Matlab simulation experiments show that when the information is abnormal,the original node can establish a new communication path to communicate with the centralized communication.4.The improved ELM wrapper feature selection method is used to detect abnormal information.In the process of anomaly information detection using intelligent algorithm,aiming at the problem of system redundancy arising from the increase of data,in order to reduce the data dimension,this paper carries out feature selection for power user information to reduce unnecessary features.By comparing and analyzing the three intelligent algorithms PNN,GRNN and ELM,the method of ELM wrapper feature selection could not only quickly find the optimal eigenvalues,but also could quickly and accurately find out the abnormal information by training and detecting the identified eigenvalues with ELM.Aiming at the influence of the number of ELM hidden layer neurons on the detection of abnormal information in the experiment,in order to find out the appropriate number of hidden layer neurons and overcome the subjectivity of setting the number of hidden layer neurons artificially,this paper uses PSO algorithm to optimize the number of ELM hidden layer neurons.At the same time,the accuracy of test samples and the running time are used as the fitness function of PSO algorithm.Experiments show that the number of hidden layer neurons identified by PSO can satisfy the shortest running time under the condition of ensuring the accuracy,thus ensuring the real-time monitoring of abnormal information.The static-dynamic combination networking algorithm proposed in this paper not only can quickly find out the optimal communication branch of each communication node in the initial networking process and overcome the problem of signal conflict,but also can dynamically adjust the key parameters by considering the time-varying random access load of the low-voltage power line channel when the original communication branch is abnormal,and find a new communication path by calculating the link index Y_i,j again.The establishment of communication reduces the impact of power line channel time-varying on network formation,improves the invulnerability and reliability of low-voltage power line communication network.