Research & Application Of Clamp Power Meter Based On DSP

It has great significance to measure real-time electric parameter accurately for ensuring state grid to operate safely and economically. So it is necessary to measure electric parameters in real-time. The paper develops clamp power meter that is based on DSP. The device may perform real-time measuring of effective value of voltage and current, frequency, power factor and power, from the second to twenty-fifth harmonic wave's frequency and amplitude.Through researching the measuring theory of electric parameter, the paper adopts discrete accumulation method to measure effective value of voltage and current signal with DSP large memory, fast operation and plentiful peripherals. Meanwhile, IIR and FIR digital filters are designed to process sample data in order to remove the noise. The paper makes use of DSP timer and multi-period synchronous frequency theory to complete frequency measuring. Using double timers to measure phase difference between voltage and current. After acquiring effective value and phase difference, according to the math formula the paper can calculate power factor and power. Harmonic analysis is an emphasis and difficulty in the paper, after comparing wavelet transformation, instantaneous reactive power and fast Fourier transform (FFT), etc. The paper uses improved algorithm for harmonic analysis based on FFT, with which the amplitudes of harmonics can be estimated from the two neighboring spectral lines. This algorithm can improve the accuracy of harmonic analysis.Based on the above measurement principle, the paper designs the measuring system of clamp power meter with the digital signal processor (ADSP-BF512) that has low power consumption. The hardware of the whole system is made of signal acquisition module, ADC module, DSP module composed of six parts, etc. The software design includes task monitoring and scheduling platform, system initialization,sampling and transporting data, data processing,keyboard and display, etc.We carry out the experiment of the meter's basic range and error analysis. The test results show that clamp power meter measurement system has good accuracy and high practical value in measuring electric parameter.