Analysis of the spectrum and amplitude error of the frequency measurement using elements of the subtraction procedure

The subject of this article is the analysis of the error introduced in the mains frequency deviation measurement by the variation of the harmonic spectrum and the amplitude of the signal. The method of frequency deviation measurement using elements of the subtraction procedure has significant advantages of fast and accurate mains frequency measurement using only a low frequency sampling rate. Although the effect of the mains signal harmonic spectrum and amplitude over the accuracy is not well analyzed. The system is implemented on Xilinx Spartan 3E FPGA. The test signal is generated with DDS signal generator and the error is examined with various signal harmonic contents and amplitudes. The results are compared to the mathematical MATLAB model. A method for error reduction using a low-pass digital filter is proposed and tested.