The Development Of Alternating Digital Source Based On Protocol IEC61850

Smart grid is the trend of grid modernization. As an important part of smart grid, substation is experiencing the transition from traditional substation to intelligent substation. Due to the requirement of smart substation, electronic transformers and merging units are widely used. The function of merging unit is according to the signal collected by the primary side, to output the message with the demand of the secondary accessing devices. In all parts of merging unit, digital source plays an significant role. As devices like digital relay protection device and digital electric energy meter analyse and monitor the operation state of grid and do the protection through digital values, it is digital source’s function to send corresponding values to such devices.Alternating digital source based on protocol IEC61850 is designed in this research and message sent from this device follows the protocol IEC61850-9-2. The digital source can not only work as simulate digital source, which can send the message accord with parameters of waveform that is set by the user, but also work as sampling digital source, which can send the message of waveform that is sampled by the system and trace to the source. To verify the message sent by sampling digital source, asynchronous sampling combined with window-interpolation algorithm based on four-term fifth derivative Nuttall window are used to measure the input signal, and the accuracy of amplitude can reach 0.05%.To meet the requirements of real-time performance and accuracy of the system, two chips of processor STM32F407ZGT6 based on kernel Cortex-M4 are used as core in this system to achieve control&calculation and message sending respectively. To achieve high precision measurement, high speed and high accuracy analog-to-digital conversion chip ADS8556 is used in system for sampling and digital temperature compensated crystal oscillator with high stability is used to ensure the sampling rate, while magnetic separation is also used to reduce the interference between signals. To achieve the communication between two processors, dual port RAM whose model is CY7C025 is used in device for data exchange. Due to the lack of PHY controller in on-chip peripherals, PHY controller whose model is DP83848 CVV is used in device to achieve network communication, so as to send packets of sampling values following the protocol IEC61850-9-2.This thesis introduces the background and significance of the research, elaborates the implementation procedure of the digital source, introduces the sampling method and window-interpolation algorithm used in sampling digital source part, then introduces the message content based on protocol IEC61850-9-2. In hardware part, combining with the schematic circuit diagram, the thesis explains design in each part of hardware. In software part, this paper elaborates the software design of digital source through program flow chart, and introduces the realization of important parts in software. At last the correctness of the output message is verified through upper computer and sampling values from digital source. Deficiencies of the system is analyzed and improvement measures are pointed out.