Improving Efficiency of DWT Analysis through Faster Interpolation Methods and Multithreading Techniques
Journal Title: ANALELE UNIVERSITATII DIN CRAIOVA - Seria Inginerie electrica - Year 2014, Vol 38, Issue 38
Abstract
The paper deals with techniques to accelerate the DWT power quality analysis. A brief description of a nonspline interpolation schematic is provided firstly. It is used for the evaluation of the first components near the right border of the signal. Comparisons were made between power quality indices, shape of details waveforms and runtimes, considering data acquired on stand, corresponding to a driving system using chopper and DC motor and respectively waveforms acquired from the secondary winding of the excitation system used to supply a generator. FFT and 3 distinct original functions were used for comparison. Similar results were generated by all methods. The spline-free interpolation technique, which used mean slopes, proved to be a better option when the analyzed signal’s periodicity is questionable, because it exhibited halved runtimes as compared to the spline interpolation technique. Two multithreading techniques, relying on a horizontal and respectively on an interleaved schematic, were afterward analyzed considering their performances relative to the DWT decomposition and respectively re-composition of single-phase currents or voltages. The analyzed filters had different lengths: 4, 6 and 8. 10 sets of 300 consecutive decompositions of signals consisting in 36864 samples were used as input data. Our Java programs implementing the horizontal technique revealed the diminishing of runtimes for all analyzed filters during the decompositions by 16%...23%, the technique being more efficient for shorter filters. Another multi-threading technique, relying on an interleaving schematic, was considered for the reconstruction of signals. It proved to be non-effective, revealing increases of runtimes in the range 19%...23%. Similar results were obtained with the horizontal technique. Finally a multithreading technique, relying on a vertical schematic is presented. Using it, savings of 45% of runtimes were revealed by tests made on three-phase systems.
Authors and Affiliations
Ileana-Diana Nicolae, Petre-Marian Nicolae, Marian-Stefan Nicolae, Andreea Chiva
Keywords
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