Influence of Harmonics on the Interpolated DFT-based Frequency Estimation for the Control of Power in Renewable Energy Systems using Generalized Maximum Sidelobe Decay Windows

Harmonic components in a multifrequency signal have a big influence on the frequency estimation accuracy and play a vital role in a power system performance. They emerge in the grid due to a large number of nonlinear loads. This paper presents a new estimation method based on Generalized MSD time windows used to analyze a grid signal distorted by harmonics in the control of grid-connected photovoltaic systems. The accuracy of the 3-point IpDFT method decreases in the presence of 3-rd and 5-th harmonics and up to two measured signal cycles there can be chosen windows for which the frequency error is at the level of 10^-4 or 10-3 Hz/Hz which is a good accuracy in real time systems. Obtained in various measurement conditions results are useful from a practical point of view as usually harmonic components are present in the grid signal.