Analysis of the impact of interpolator's order on the accuracy of electric current spectrum estimation method in the presence of noise

In the nonlinear analysis of electrical power supplying networks, it is often necessary to determine the frequency domain model of the network. This model is usually determined from time domain measurement data. One of the most demanding tasks is to determine the frequency spectrum of the currents flowing through the nonlinear elements with sufficient accuracy. The paper describes the results of the accuracy analysis of an electric current spectrum estimation method. The method is applied using different orders of Newton's interpolator to restore the optimal sampling parameters of a noisy signal. The presented frequency spectrum estimation method is characterized by its high accuracy in comparison with similar methods, such as WIFTA (Window Interpolated Fourier Transform) or TDQS (Time Domain Quasi-Synchronous Sampling), while still being relatively fast when contrasted with higher order Prony's methods. The conducted research shows that the accuracy of the method evidently depends on the order of the Newton's interpolator and best results, in terms of accuracy and computing power, are achieved for interpolator's order equals 7.