| With obvious improvement of transmission capacitance and rated voltage in power system,traditional electromagnetic transformer have emerged serious drawbacks and have been already difficult to keep up with the development of power system,so it is unavoidable that electronic transformer substitutes old electromagnetic transformer.Due to the different output forms between electronic transformer and traditional electromagnetic transformer,how to design the communication interface in the processing level in substation becomes the key problem in research processes.In addition,power supply for electronic circuit at the high-voltage part is also an important technique in research and applications of electronic transformer system.The realization methods of the digital output for electronic transformer is researched according to IEC60044-8 and IEC61850 standard in this paper,and the major topic is composed of encoding module,decoding module and digital signal processing module of processing level.FGPA,which has high integration and flexible programming,is used as microprocessor in encoding module and decoding module of processing level,these modules complete framing by adding the multisampling data, the frame head and CRC code together,then the data frame is encoded on Manchester code and transmitted to merging unit of processing level by using fiber technology. The circuit of decoding module is designed by using the rich bit timing information characteristic of Manchester code,which is used to collect the multi-channels data, unpack the data frame and check.The digital signal processing module of processing level uses DSP as its microprocessor,which completes collecting the multi-channels data stream from electronic transformer at the first,then merges processing and codes the data after packing total frame according to the IEC61850-9-1 standard,transmits these data to bay level by RTL8019AS at the final.Because of the problem of power supply for those active electronic elements at the high-voltage part,a power supply which combines a self-supplying power source with an optical power is proposed,and the auto-switch technique is designed between the two supplies in the paper.Driving circuit and protect circuit in source driver system of semiconductor lasers are designed in order to improve the stability and reliability of laser powered system,and the algorithm of fuzzy self-tuning PID was adopted to improve the high-precision of controlling temperature for laser diode.The results of simulation proved that the proposed methods can settle the problems such as digital communication of electronic transformer,power supply for those active electronic elements at the high-voltage part,which can provide some experiences for practical application of electronic transformer in substation automation system.It is an unavoidable trend that digital substation using electronic transformer,fiber communication and computer will be used in future substation system. |
