An Improved PRBS-Injection-Based Grid Impedance Measurement Method Considering Nonideal Grid Conditions

The wide-bandwidth grid impedance measurement is a vital way in the resonance and stability analysis of the grid-tied system. However, the grid inevitably suffers from some nonideal conditions, such as voltage unbalance, frequency deviation, harmonics, and interharmonics, which has not been fully considered and well handled in grid impedance measurement using pseudorandom binary sequences. To address this challenge, a three-stage interpolation-based measurement method for grid impedance measurement is presented in this letter. The proposed method adopts the cubic spline interpolation to reconstruct the sampled signal and use the Hanning-window-based interpolated fast Fourier transform (FFT) to remove some undesired components to deal with the spectral leakage caused by the FFT. Simulation and hardware-in-the-loop experimental results are presented to demonstrate the performance of the proposed method.