The Research Of Electronic Transformer And Merging Unit

There are many defects in traditional substation：devices from different manufacturersare difficult to achieve interoperability, a large number of cables are needed to transmit analogdata, the low voltage devices can not be insulated from the high voltage devices,so theinsulation design is difficult. The traditional substation is unable to meet the demands of thedevelopment of the power system. Digital substation has a certain basis with the technicaldevelopment. Electronic transformer and its universal digital interface-Merging Unit(MU)are the key parts of the digital substation, which have a strong research significance.This paper first analyzes the research background and significance of the digitalsubstation and MU, builds the overall structure according to the functional designrequirements of MU.Then demonstrates the design of the digital transformer which takes theMSP430microcontroller as control core. And then the paper explains the detailed structure ofthe MU based on ARM&FPGA, introduces the hardware circuits including the interfacecircuits between ARM and FPGA,ARM and the network controller DM9000， analyses thesoftware realization of synchronous sampling control, receiving and processing data indifferent channels and the Ethernet communication. Again, to meet the requirements of strongreal-time, high reliability, strong anti-interference capability in the digital substation, thetransplant of embedded operating system in MU is studied.Finally, experiments on the electronic transformer and its MU are conducted. The outputcharacteristics of the electronic transformer, the packet format of the MU output data and thepacket loss rate are tested. In order to verify the overall performance, the output data of theMU are sent to the calibration system with the ratio error and the phase error checked.Experimental results show that the proposed design satisfies the requirements of real-time,interoperability, and reliability and possess certain practical value in engineering.