Research On Power Quality Data Compression Algorithm

As the power quality problem has attracted increasingly widespread attention of the whole society, requirements on power quality monitoring system have also been enhanced. Power quality monitoring system is also developing towards intelligence, remote and virtualization. The power quality itself covers a wide spectrum and therefore a higher sampling rate is needed to collect power quality data. Meanwhile, in order to realize the intelligent and remote monitoring system, such large amounts of data need to be transmitted. To decrease the data storage space and reduce the transport cost in the process of communication, in-depth research is required to study the application of data compression technology in the power field.This paper first introduces the power quality to have a further understanding of the characteristics of power quality and choose the appropriate compression algorithm in allusion to the characteristics of power quality. Meanwhile, in the research process of Fourier analysis and wavelet analysis, it is found that Fourier analysis has a better analysis effect on steady-state signals, while the wavelet analysis has characteristics of both time-frequency analysis and multi-resolution analysis. Therefore, the wavelet analysis is quite fit for the analysis of transient signals. Combining the characteristics of the power quality and corresponding advantages of Fourier analysis and wavelet analysis, this paper adopts the lossy compression algorithm based on the combination of Fourier transform and wavelet transform. In the process of lossy compression of signals, each piece of data is processed with signal detection by wavelet transform through the signals’ segment treatment. If a signal is determined to be steady-state and steady-state disturbance one, the Fourier transform compression will be conducted on it. If the signal is determined to be transient disturbance signal, the wavelet transform compression will be adopted.In order to further improve the effect of compression, lossless compression is further required to conduct on the processed data through a lossy compression algorithm. After comparing two kinds of widely used lossless compression algorithms, Huffman coding based on statistical model and LZW algorithm based on the dictionary model in the field of the lossless compression, this paper analyzes their characteristics respectively and eventually adopts the LZW algorithm with better real-time performance as a lossless compression algorithm. At the same time in order to conform to the developing trend for virtualization and in line with the thought of “software is an instrument”, power quality data compression algorithm is finally realized on Lab VIEW based on FFT and the combination of wavelet transform lossy compression and LZW lossless compression to make the algorithm practically applied in the virtual instruments.In addition, on the Lab VIEW platform, the paper presents simulations of three kinds of common steady-state disturbance signals and five kinds of transient disturbance signals and compresses a period of simulation signal with harmonic disturbance, oscillation disturbance and noise by using three compression algorithms respectively, the algorithm in this paper, Fourier transform compression algorithm and wavelet transform compression algorithm. It is testified that the algorithm proposed in this paper has a better compression effect by comparing the results.