A Harmonic Impedance on Utility Side Estimation Method Based on Laplace Mixture Model

With the advancement of new power systems, an increasing number of new energy power stations and nonlinear loads are connecting to the grid. This has led to a more serious problem of harmonic pollution, with an increase in harmonic sources within the power grid. Estimating the harmonic impedance on the utility side is crucial for assessing harmonic emissions and evaluating harmonic contributions. However, existing methods have some shortcomings in terms of estimation accuracy and robustness. This paper proposes a method for estimating harmonic impedance on utility side based on the Laplace mixture model (LMM) to address these issues. In the proposed method, the LMM of the utility side harmonic current is formulated, and the harmonic impedance on the utility side is subsequently estimated using the maximum likelihood estimation (MLE) and expectation maximization (EM) algorithms. The proposed method demonstrates high estimation accuracy, as it exhibits smaller estimation errors in both simulation and field test cases compared to other estimation methods. Furthermore, even when background harmonics are significant, the proposed method maintains its accuracy.