Método de estimação de impedância utilizando a injeção de pequenos sinais

Abstract

This work proposes a method to estimate the power grid impedance in an invasive form, using a disturbance control structure, a filter to eliminate the harmonic components contained in the power grid and an interpolator in case of frequency variation. The impedance is an important parameter for the power grid stability analysis because through its estimation it can be verified, for example, if there is the presence of resonance. To insert the disturbances in the voltage and current signals, the Gaussian Modulated Signal (GMS) is used, which may have its decay controlled by the function parameters. Regarding the presence of the harmonic components, which influence the estimation of impedance, a version of the Sliding Window Recursive Discrete Fourier Transform (SWRDFT) is proposed to estimate and eliminate these components in order to remain only the disturbance signal. Regarding the frequency deviation, another issue that affects the impedance estimation, an interpolation structure is proposed, using the Lagrange method. The function of the interpolation is to establish the synchronization of the current and voltage signals before being processed to determine the impedance value. To validate the results, tests with grids on Simulink, RTDS, dSpace and using an experimental circuit are performed. Results consider Electrical Systems with resonance, with the presence of background harmonic components and frequency variation. For all cases, the estimation results were satisfactory.