Method of Reducing the Amplitude and Phase Spectrum Measurement Error of the Power Quality Measuring Instruments

The absolute majority of power quality parameters are measured indirectly through the signal complex spectrum. For this reason, amplitude and phase spectrum accurate measurement is of the utmost importance. Discrete Fourier transform is most commonly used to measure the complex spectrum. The complex spectrum measurement error is associated with so-called “spectrum leakage” effect. The paper proposes a method to compensate of the “spectrum leakage” effect, based on additional frequency measurement and calculation of tuning coefficients for complex spectrum. The features of the application of the proposed method for the case of sinusoidal and polyharmonic signals are considered. Modifications are proposed for the case of applying the fast Fourier transform algorithm (FFT) and Goertzel algorithm. Analytical relations are obtained, which make it possible to estimate the amplitude and phase spectrum measurement error. By applying Matlab, simulation modeling has been performed, which makes it possible to evaluate the effectiveness of proposed technique.