With the development of smart grid, a lot of nonlinear loads and new energy power stations are connected into the power network. There are a large number of harmonic sources in the power grid, harmonic distortion has become one of the main power quality concerns in recent years. Utility side harmonic impedance estimation is important for evaluating harmonic emission levels and determining the harmonic responsibility. In the traditional methods, the harmonic voltage and current at the PCC are considered to satisfy the normal distribution and the timing correlation of them is ignored which contains important information that can be used to estimate the harmonic impedance. This paper proposes a new method for harmonic impedance estimation based on the Burg algorithm and AR model. In this paper, harmonic voltage and current are considered to satisfy AR model including timing correlation. The reflection coefficient is calculated by minimizing the average power of the forward and backward errors in the AR model. Then, the utility side harmonic impedance is estimated by minimizing the apparent power. The proposed method is robust, and the error of the estimation result is small by the proposed method. Whats more, the proposed method is not limited by some traditional assumptions, such as the background harmonics are stable and small, the customer harmonic impedance is much larger than the utility, and the harmonic sources of both sides are independent, and so on.
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