Evaluation of the Effect of Successive Approximation ADC Nonlinearity on the Measurement Error of the Phase Spectrum

The phase spectrum is the power quality parameter. The value of this parameter is used for indirect measurement of phase difference between signal spectral components, active and reactive power of the signal. Among digital methods of spectrum measurement the most popular method is based on the application of the discrete Fourier transform (DFT). To obtain samples of the signal requires analog-to-digital converter (ADC). The transform function of a real ADC is nonlinear, which results to a measurement error. The nonlinearity of the ADC built by the successive approximation architecture in form close to a random function. For this reason, existing methods of estimating the measurement error of phase spectrum from ADC nonlinearity results to a strong overestimation of the error values with respect to simulation results. In the present work, the methodology of estimation of the phase spectrum measurement error caused by the nonlinearity of the successive approximation ADC is developed. The nonlinearity of ADC is presented as a random function. The comparison of the proposed method with the popular method of "worst case" is done. Simulations by the software package Matlab is performed.