| Multifunction Supply Network Harmonic Analyzer is an electrical measurement meter which is used to measure, calculate and display supply network parameters, such as harmonics of voltage and current, voltage, current, power frequency, active power, reactive power, power factor etc. With the rapid development of the automation in power system, more and more nonlinear equipments have been used in the supply network, the generated large amount of high-order harmonic current has been injected into the power system that results in waveform distortion of voltage and current. So that,the real time supervisory and measurement of the harmonic content in the supply network and acquiring the harmonic actualities are significant to prevent harmonic harm and maintain the supply network running safely.This paper uses the ARM7as the core process unit, researches deeply the harmonic measuring algorithm and the design of embedded software and applicates them in the development of Supply Network Harmonic Analyzer system. Based on the comparison between basic harmonic analysis algorithms, the DFT and FFT algorithm based on synchronous sampling have been studyed.Considering the asynchronous sampling in practice, the influence on the power system harmonic analysis has been analysed, and the window-function method to reduce the synchronous sampling error has been researched. This paper simulates and realizes FFT with Hanning-window as its core algorithm. At the same time,based on the analysis to the function of harmonic analyzer,the hardware circuit based on this algorithm has been designed and the embedded software program based on modularization has also been realized.The results show that this algorithm and hardware design have satisfied the requirements of reality and precision.Also the communication based on MODBUS protocol is achieved to realize the real-time monitoring of the electrical parameters.The author believes that The supply network harmonic analyzer will be prosperous in the power system. |
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