| Under the new situation of the development of new energy technologies and systematically exploring smart grid implementation approach in our country, this paper based on the background of development of high performance power quality monitoring device. The materials of domestic and international power quality monitoring devices are extensively referenced. A fast, real-time, high-performance power quality monitoring device was designed. The monitoring device selects DSP2812 as the microprocessor to monitor the three-phase voltage and three-phase current. The sampling data voltage deviation, requency deviation, harmonic and three-phase unbalance was calculated and analyzed in real-time. Sampling data and analytical data was transmitted to the host compu-ter together by CAN bus communication. Host computer analyzes, calculates and counts in real-time through a visual interface to show grid status intuitively. At the same time, human interface module displays power quality indicators real time in next machine. The concrete work is as follows:(1) The research status of power quality monitoring devices at home and abroad was introduced. The definition of power quality was given. The power quality indicators and the detection method were discussed.(2) Hardware circuit design was completed, according to the monitoring device design requirements on data acquisition, analysis, upload and display. A schematic and PCB diagram of power quality monitoring device were drew. Hardware circuits include data acquisition module, main controller and its perip-heral circuits, human-machine interface module and communication module.(3) The software of the system was designed with the idea of object modu-larization. The main program and the functional sub-module program were programmed with C language. The three-phase voltages and three-phase current data were sampled with interrupt technology in real-time. CAN bus comm-unication was adopted. The data collected and analyzed with inquiry mode was transmitted to the host computer by CANET module. The device use buttons to realize the function about up, down, enter and return. FYD12864 LCD module displays power quality indicators information in real-time. In lower machine, device detects four key indicators of power quality, analyzing frequency devi-ation by zero-crossing detection algorithm, harmonic by FFT and three-phase unbalance by symmetrical components method.(4) The principles of digital filter were outlined. Several structures and advantages and disadvantages of filter were introduced. Software digital filter’s realization in DSP was analyzed in detail. The method used was a combination of Matlab and DSP. First, filter was designed on Matlab and filter coefficients table was imported into CCS. Then filter program was written on CCS. Last, the correctness of the filter was verified design by inputting analog functions.(5) The realization of the fast Fourier algorithm in lower machine was ana-lyzed. The basic principle of the FFT and DFT and the derivation of the FFT algorithm were described. Fixed-point DSP realization of FFT was elaborated. Correctness of the FFT algorithm was verified by simulating the sine function. Then the condition of harmonic changes was monitored in lab network and power grid containing high power nonlinear element in real-time. Research and development of power quality monitoring device in this article meet design exp-ectations and has some practical significance. |
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