Study On The Delay Of CAN Bus At The Process Level Of Substation And Distribution And Its Node’s Realization

CAN bus is a good choice of the process level of transformation and distribution for its low cost, high reliability, easy maintenance and many other advantages of the implementation. With the increasing size of communication networks and complexity of power distribution automation system, the real-time data communication system requirements are increasingly stringent, So It is very important to analyze delay characteristics of the CAN bus. On the basis of summarizing and reviewing the development of the process bus, learning the basic theory of real-time scheduling, the thesis commits the analytical work of the CAN bus’delay characteristic, and designs a table-based dynamic priority promoted CAN node.(1) The thesis analyzes the process level of transformation and distribution and the CAN bus’current situation and development trend. In the meanwhile, it points out the limitations of standard CAN protocols. Then,It elaborate that studying on the delay of CAN bus is very necessary. And on the basis of this, the thesis makes research on power distribution station communication real-time system technology infrastructure.(2)From Media access technology of CAN bus, the thesis analyzes the existing real-time problem of low-priority packets under the high bus load rates, and quantitatively analyzes the worst response time of the data transmitted in the communication network. The thesis analyzes and compares the table-based static promotion methods and dynamic priority methods, a table-based dynamic priority promotion method is proposed. Mathematical analysis shows that the method has theoretical feasibility.(3)Under the CAN Agreement International Standards, Corporate standards and functional requirements of the project, CAN node module design requirements and overall design are proposed. Under the core of LPC2119, the hardware system consists of the interface module, serial interface module, power module, man-machine interface module, and debugs modules etc. Each module is described from the circuit architecture and its realization in detail. Combining hardware circuit, the Software system takes advantage of C language and Keil’s uVison3development environment, to describe the table-based dynamic priority approach in detail.(4)Combination of enterprise distribution platforms and intelligent circuit breakers, the thesis takes advantage of USB-JATG to repeat testing of the CAN prototype. Test results are given to verifie its performance and functionality. Final test and operation results show that the proposed table-based dynamic priority algorithm is workable. The designed CAN node prototype based on this method operates stably. The relevant indicators of technical capabilities achieve the desired design requirements.