عنوان مقاله
تراکم داده به منظور کنترل کیفیت توان الکتریکی بار کوره قوسی
فهرست مطالب
مقدمه
تبدیل موج کوچک
فشرده سازی و رمزگذاری داده
روش رمزگذاری کوانتش برداری (VQ)
کاربرد اندازه گیری اشکال موج به روش میدانی
نتیجه گیری
بخشی از مقاله
فشرده سازی و رمزگذاری داده
هدف از فشرده سازی داده ها، کاهش تعداد داده ها به منظور بیان اطلاعات سیگنال با حذف داده های کپی شده می باشد. مفهوم اصلی در شکل 1 شرح داده شده است،، در اینجا، C0[n] سیگنال اصلی ( اشکال موج جریان و ولتاژ اندازه گیری شده ) و C0[n] سیگنال بازسازی شده می باشد (اشکال موج جریان و ولتاژ بازسازی شده). فرایند فشرده سازی داده های رمزگذاری شده را C0[n] نامیده (اشکال موج جریان و ولتاژ ذخیره شده) و به همین خاطر فرایند بازسازی از داده های رمزگذاری شده استفاده می کند.
کلمات کلیدی:
DATA COMPRESSION APPLIED TO ELECTRIC POWER QUALITY TRACKING OF ARC FURNACE LOAD Chi-Jui Wu* and Tsu-Hsun Fu** Paper Submitted 12/26/02, Accepted 04/01/03. Author for Correspondence: Chi-Jui Wu. *Professor, Department of Electrical Engineering, National Taiwan University of Science and Technology, Taipei, Taiwan, R.O.C. Professor, Department of Electrical Engineering, National Taiwan Marine University, Keelung, Taiwan, R.O.C. **Associate Professor, Department of Electrical Engineering, Chin-Min College, Miaoli, Taiwan, R.O.C. Key words: electric power quality, data compression, discrete wavelet transform, multi-resolution analysis, coding. ABSTRACT The data compression techniques are used to enhance the storage capability of electric power quality instruments in monitoring distorted waveforms of electric arc furnaces. Both voltage flicker in voltage waveforms and harmonic components in current waveforms are major disturbances. The compression approaches by multiresolution analysis developed from the discrete wavelet transform with threshold coding and vector quantization coding are compared. The results from spectrum analysis show high compression ratios while keep low information loss. The error levels between original and reconstructed waveforms are discussed. Field measured waveforms from arc furnace loads are used to show the goodness of the data compression techniques. From the calculation results, the reconstructed voltage waveforms using threshold coding almost keep the same voltage flicker values. However, the vector quantization coding is better for harmonic distorted current waveforms. Thereafter, in the practical application of data compression for arc furnace loads, the threshold coding is used for recording voltage waveforms, and vector quantization coding for current waveforms. For the field measurement voltage and current waveforms, this method can reduce data memory size to 15.11% and 24.51%, respectively, while keep power quality characteristics. This paper provides a good approach to longtime electric power quality tracking of disturbing loads. INTRODUCTION Fluctuating loads, such as electric arc furnaces and electric welders, may cause the disturbances of voltage flicker (voltage fluctuation) in a weak power system and affect the illumination in nearby distribution area [5]. By the way, not only the DC arc furnaces, but also the AC arc furnaces will produce harmonic currents. Both
