Effects of Sampling Rate and ADC Width on the Accuracy of Amplitude and Phase Measurements in Power-Quality Monitoring

The effects of analog-to-digital conversion (ADC) quantization noise on the recovery of harmonic amplitudes and phases in the presence of large fundamental amplitudes are examined by theory and simulation, in order to determine the noise limits of instrumentation system design for power systems monitoring and harmonic power-flow measurement. Amplitude and phase errors are independent of the harmonic order; the amplitude error is independent of harmonic amplitude for sufficiently large signal-to-noise ratios; and the phase error is inversely proportional to harmonic amplitude. The noises may be reduced by increasing the ADC width or the transform length. Graphs are presented which show the various tradeoffs which can be made, in particular, between harmonic phase recovery and ADC width