The Study Of AC Data Acquisition And Its EMC Performance Based On DSP

It is the important data source of monitoring the running state of the power system that the AC data acquiring in power plant or substation automation system. In the course that data is obtained by way of AC sampling, should settle problems of electric signal transforming, A/D converting, and voltage, current, frequency, true reactive power and harmonic calculating, could guarantee in this way the final output data precision and response speed meet the stated requirements. In hardware and software design of AC sampling equipment, but also needs key to solve the electromagnetic compatibility(EMC) performance of equipment especially, in order to improve anti-interference level and reliability of the equipment.The paper has mainly analyzed in the AC data acquiring system based on the DSP56F807 hardware principle design, the sampling precision, the true reactive power calculation problem as well as improvement frequency measurement precision. In the software and algorithm design, the paper has made up the ADC itself 12 bits weak resolution, increased the final data output precision, by using "over sampling" principle, integrating high speed of DSP56F807 and the FFT algorithm which DSP excels, and by sampling in rate of 128 points per cycle and computating on whole cycle. At the same time, by using the high sampling rate and the FFT algorithm, the paper has carried on the computation of various harmonics U, I, P, Q, Cos Φ, thus guaranteed finally the true reactive power computation correctness and precision. In frequency calculation, the paper takes the positive sequence component as the foundation data, uses the Fourier frequency measurement principle to measure the frequency, thus enhances the frequency measurement stability and precision.In the EMC aspect, from designs of earthing, ground system, shield, filter, PCB, software design, and so on, the paper systematically improves the equipment the whole EMC level, also only then like this, can the very good EMC solution be solved, and made EMC test pass through the severe examination rank. The paper has conducted the research to unipolarity ADC on the 2nd order front filter, and by using the Pspice software to carry on the analysis on the filter effect under different noise source, obtained the optimal filter design method under the similar application.