Utility harmonic impedance estimation considering unsmooth fluctuation characteristics of background harmonics

• Multiple abrupt changes of background harmonic voltage and impedance are identified through the binary sliding T-test method characterized by the adjustable window width and multiple screening. • Utility harmonic impedance estimation under unsmooth variations of background harmonics is achieved by minimizing the comprehensive fluctuation of background harmonic voltage and impedance. • The time complexity of utility harmonic impedance estimation is decreased by the sparse matrix technique that exempts zero elements from participating in matrix operations . • The proposed method is competent to promote the accuracy and efficiency of utility harmonic impedance estimation in scenarios with unsmooth background harmonic fluctuations. Accurate estimation of utility harmonic impedance is key to harmonic source determination and harmonic mitigation. Most existing methods depend on the premise that the background harmonics remain constant or fluctuate smoothly, but in practice, the background harmonic voltage and impedance usually exhibit unsmooth variations or even abrupt changes. In light of this issue, this paper proposes a two-stage method for utility harmonic impedance estimation considering unsmooth fluctuation characteristics of background harmonics. In the first stage, multiple abrupt changes of background harmonics are identified through binary sliding T-test to segment the recorded harmonic voltage and current. In the second stage, the utility harmonic impedance is estimated by comprehensive minimum fluctuation and matrix sparsity within each recorded harmonic data interval. Simulation and field case studies are performed to verify the efficacy of the proposed method. The results demonstrate that this method surpasses other previous methods in computational accuracy and efficiency. Moreover, superior robustness against drastic background harmonic fluctuations is also exhibited.