Title :
Total harmonic distortion calculation by filtering for power quality monitoring
Author :
Mog, Gérson Eduardo ; Ribeiro, Eduardo Parente
Author_Institution :
Inst. of Technol. for Dev., Univ. Fed. do Parana, Curitiba, Brazil
Abstract :
Measuring and monitoring quality parameters of AC power systems requires several calculations, such the total harmonic distortion (THD) of voltage and current. This calculation is performed with samples of the monitored waveforms, at sample frequency equal to a power of two multiple of the frequency of waves. The samples are converted to digital values by analog-to-digital converters, with a finite number of bits. Numeric algorithms applied to these digital values insert some errors in the final results, due to the number of bits used in calculations. The most used algorithm to obtain the THD is FFT. Conventional 16-bit DSP FFT algorithms use only 16-bit calculations, despite the DSP 40-bit hardware accumulator. The results are errors in amplitude of each harmonic order. Using these amplitudes to calculate the THD, these errors are summed, and the final error is very greater. The purpose of this article is to present an algorithm to calculate the THD using the DSP 40-bit hardware accumulator and resulting more accurate results.
Keywords :
analogue-digital conversion; digital signal processing chips; discrete Fourier transforms; discrete time systems; harmonic distortion; measurement errors; power supply quality; power system analysis computing; power system harmonics; power system measurement; sampled data systems; AC power system; DSP 40-bit hardware accumulator; FFT; THD; analog-digital converter; current distortion; digital values; discrete Fourier transform; discrete time system; fast Fourier transform; harmonic order; measurement errors; power quality parameter measurement; quality parameter monitoring; sampled data systems; total harmonic distortion; voltage distortion; waveform monitoring; Digital signal processing; Filtering; Frequency; Hardware; Monitoring; Power filters; Power harmonic filters; Power quality; Power system harmonics; Total harmonic distortion;
Conference_Titel :
Transmission and Distribution Conference and Exposition: Latin America, 2004 IEEE/PES
Print_ISBN :
0-7803-8775-9
DOI :
10.1109/TDC.2004.1432452