The Researching And Design Of The Merging Unit In Digital Traction Substation Based On FPGA

With the rapid development and promotion of smart grid technology, digital devices and intelligent devices are widely applied to practical smart grid projects. Compared with power system, the development of traction power system is slower, and traction substation is still in the stage of integrated automation. However, the digital technologies such as the electronic transformer technology become more and more mature that speed up the digitalization and intelligent of traction substation. Compared with power system, the inputs of the merging unit (MU) has its particularity in the digital traction substation. Therefore, the research and design of MU of digital traction substation is of great importance.For the digitization scheme for traction substation, the configuration of transformers and MU is a key research point. Referring to the experience and configuration of the power system, the technical requirements and configuration principles of transformers and MUs in traction substation are given. Then a specific configuration scheme is presented according to the diagram of typical traction substation. Considering the network structure of simple value (SV) is point-to-point transmission and GOOSE networking in traction substation process level, the interfaces and functional requirements of MUs are analyzed. Finally, FPGA is chosen as the core unit of overall hardware design of MUs that include the data acquisition module, the data processing module and the data sending module.For the data acquisition module, it specially requires MU to receive analog signal from traditional transformer and digital signal from the ECT/EVT. The key technology is to realize various data synchronization. Using A/D control module, analog signal is converted to digital signal. The synchronization scheme is determined by analysis of pulse synchronization and interpolation synchronization. Based on FPGA, the sub-modules designed for this paper include resolving FT3, checking the validity of1PPS, linear interpolation, FIFO, A/D controlling, etc.For the data processing module and sending module, this design takes advantage of fast data processing and abundant resources by FPGA instead of DSP. By analyzing the principle of digital filter, phrase compensation algorithm (digital integrator and short data window phrase-shifting algorithm) and RMS calculation, the data processing module has been realized by FPGA. On the basis of description of IEC61850-9-2packets, the Ethernet communication mechanism is elaborated especially for the design of MAC. Finally,9-2message sending module is completed by FPGA.For the three modules above, each module is simulated and verified by Xilinx ISE13.1, Matlab and other software, and some functions of MU is tested by MRT. The results show that the proposed scheme for MU of digital traction substation is efficient and has some potential in practical engineering.