Research Of Merging Unit Based On Iec61850

IEC61850 is presently the most perfect communication protocol standard in substation system, which presents basic theoretic foundation for realizing digital substation. As one of the key devices in process bus of IEC61850 system, merging unit (MU) resolves the problem of digital interface between electronic transformers and secondary devices, containing protection, measurement and control devices. The research of it will bring great significance to the popularization of electronic transformers and the practice of IEC60850 protocol standard.In this paper, the chief characteristic and core conception of IEC61850 is described at first. On the basis of these analyses, the modeling and mapping of MU is discussed, which helps understand the main functions of MU. In order to achieve theses functions, a universal scheme of accomplishing MU is then presented, which takes the diversity of sensor principle and the flexibility of communication protocol into account. To implement this scheme, a circuit based on AT91RM9200 micro processor is designed, in which the model of data collecting and processing is aimed to active electronic transformers. However, the circuit can be easily expanded to interface other kinds of electronic transformers. The course of the circuit debugging is also discussed, including some personal experience during the course. After that, the method of program design based on this circuit is discussed. Two kinds of program, boot program which contains self-boot, U-Boot and internal-boot and application program to implement the functions of sampled values transmission and digital scalar based on IEC61850-9-1, is introduced in this part. At last, the method of testing MU'main performance is introduced, the result of which proves that the hardware and software system designed in this paper can absolutely realize the functions of MU in IEC61850-9-1, and the hardware system can also meet the need in IEC61850-9-2.