Study And Implementation Of Electric Power Data Compression, Transmission And Decompression Algorithm

With the advancement of transformer substation automatization technology, the amount of data gathered by such monitoring devices has become huge in size. Hence tremendous amount of data transmission and storage has become an issue of utmost importance and need to be solved urgently in power system. The most effective method to resolve this problem is to compress the monitored data. Considering the excellent features of wavelet transform in the time and frequency domain, the data compression algorithm based on wavelet transform was proposed in recent years. This algorithm could not only obtain high compression multiple, but also reconstruct original signal accurately. But according to the present research, there were still some theoretical and technical problems that limited the practical applications of this algorithm. For instance, the compression algrithm based on first generational wavelet transform demanded large amount of computation, which made it not feasible to hardware and real-time implementation; when using second generational wavelet transform, the Euclidean decomposition was not one and only, the reduce of computation was limited and the orthogonality of wavelet filter bank was weakened during the process of lifting.Considering the problems above, the electric power data compression and decompression algrithms based on wavelet transform and the remote transmission technology of compressed data were deeply researched in theory and tested with mass experiments in this paper, the main tasks are below:1,Firstly, the method to apply data compression technology in electric power system was introduced. The principle of compression and the evaluation criteria of compression algorithms were discussed. And the mathematical models of electric power signals were established.2,A novel bitmap compression algorithm to record nonzero wavelet coefficients was proposed for the first time. Compared with traditional threshold value algorithm, the proposed algorithm can obtain higher compression multiple when the reconstructive signal with the same mean square error.3,On the basis of analyzing integer lifting process in depth, an improved integer wavelet threshold compression algorithm was proposed for the first time. It can effectively settle the problems, such as the complex realization, the low speed and the floating-point resulting filtered outputs, which are brought by the compression algrithm based on first generational wavelet transform. Compared with first generational wavelet compression, the performance of new approach is enhanced at three aspects, which are the energy recovery coefficient, the mean square error of reconstructive signal, and real-time property of compression algorithm.4,Considering the features of power system data, a Ray-Period compression algorithm based on integer wavelet transform was proposed, where the low-frequency data was processed by lossless Ray-Period algorithm. The algorithm further increases the compression multiple of integer wavelet threshold compression with the same mean square error.5,An efficient algorithm to build integer arithmetic wavelet transform (IAWT) was proposed by improving the traditional wavelet filter structure and coefficients, which solves the problem of the floating-point computations essentially. By applying IAWT to compress data in power system, the computing speed of algrithm is greatly increased. Then the compression method of gray and true color image was researched preliminaryly.6,Through compared the present ways of remote transmission, GPRS was chosen to transmit the monitoring data in power system, which greatly increased the flexibility of data transmission. Then the remote transmission scheme based on GPRS was proposed and demonstrated in detail from the selection of GPRS module, network access and transmission protocol. Based on the above, the application level protocol was designed, which further enhances the reliability of transmission.7,The software and hardware development platform of remote data transmission scheme based on GPRS was built, among which the monitoring terminal was an embedded development board using S3C2410A processor with ARM920T kernel and Windows CE operation system, the MC55 module was connected to the board via serial communication interface. Using EVC4.0 and C/C++, the programs that consist of data compression, decompression and GPRS data transmission were designed and realized, a friendly graphical interface was given and multithreading technology was adopted in GPRS transmission. Mass of network transmission testing result confirms the reliability and stability of our transmission programs.The compressed data receiving could be reconstructed with the aid of inverse wavelet transform. So the section of data decompression wasn't discussed solely in this paper, its principles and flow charts had been introduced together with data compression. The experimental results prove that the algorithms proposed in this paper are correct and effective.