Fast and Accurate Harmonic/Interharmonic Parameter Estimation in Modern Power System: A New Approach

The dominance of the interharmonic components is going to increase in the electrical power system due to the use of modern equipment. Fast Fourier transform (FFT) fails to give accurate results when interharmonics are present in a signal. The estimation of signal parameters via rotational invariance technique (ESPRIT) is one of the parametric methods that can be used for parameter estimation and has very high resolution, but suffers from high computational burden. Thus, there is a need for a method that has low computational burden with high accuracy. This article uses an idea to estimate the integer part of the frequency component using FFT and, if required, a fractional part is calculated using a hybrid Aboutanios and Mulgrew q-shift estimator (HAQSE) algorithm. The HAQSE algorithm interpolates between two frequency bins to reach close to the actual frequency component. A Poincare-plot based periodicity filter has been used to detect the presence of interharmonic components and select the algorithm accordingly. To show the effectiveness of the proposed method, a comparison has been made in terms of accuracy and estimation time required by the algorithm with respect to parametric method. The proposed method is tested using synthetic and practical signals from a welding machine and air compressor. Relative root-mean-square (rms) reconstruction error (RMSE) is calculated to show the accuracy of the proposed estimation technique. Since the proposed method is computationally less burdened, this makes it compatible with low-cost hardware for online monitoring of harmonics/interharmonics in emerging electric power systems.