Traffic Flow Modeling And Timeliness Research Of New Generation Intelligent Substation

The new generation intelligent substation is a substation with "highly integrated system,reasonable structure layout,advanced and applicable equipment,energy-saving and environment-friendly economy,and integrated support for regulation and control" as the goal.As the carrier of information data such as electrical quantity and the application function such as relay protection,the timeliness of substation communication network（SCN）traffic flow not only determines the effectiveness of substation secondary system control decision,but also affects the safe and stable operation of power primary system.A reasonable and effective substation communication network scheme helps realize efficient and reliable data transmission and interaction,so as to ensure the traffic flow timeliness requirements.However,the current analysis and design of SCNs mainly rely on the empirical judgment of designers or the estimation of time delay,and lack scientific analysis and argumentation.Therefore,in this thesis,we conduct mathematical modeling and quantitative analysis of communication delay based on the perspective of traffic flow.Firstly,we analyze the mechanism of traffic flow transmission delay and find that the random queuing situation at the switch due to bandwidth competition leads to uncertainty in the delay.After clarifying the upper bound of transmission delay on different types of traffic flows,based on the phenomenon of deterministic timeliness requirement and uncertain transmission delay of deterministic traffic flow in SCN,we propose to quantify the uncertain delay by upper bound of delay,and use network calculus as a tool to carry out the quantitative study of upper bound of delay.In order to quantitatively calculate the delay upper bound of traffic flow,using the idea of power flow calculation for reference,the communication network parameters are defined as injected traffic,equivalent rate and delay upper bound,and mathematical tools such as graph theory and matrix analysis are introduced to propose a traffic flow modeling method based on network algorithm,which can solve the upper bound of delay of each path of traffic flow at each port and end-to-end upper bound of delay by algebraic equations.It provides a simple and clear quantitative means for timeliness research.In order to improve the pessimism of the evaluation results of the end-to-end delay upper bound based on the traditional network calculus,the traffic flow queued at the port is divided into effective competitive flow and invalid competitive flow.A deterministic calculation method of delay upper bound based on effective competitive flow and a communication network performance evaluation method are proposed,which can be used to analyze the communication network performance through the delay upper bound and port criticality index.It can provide a quantitative reference basis for the design of communication network configuration scheme and the selection of equipment models.