Estimating background harmonic voltage and equivalent harmonic impedance at the point of common coupling (PCC) is the premise of studying harmonic contribution determination. For the purpose of accurately assessing harmonic contributions of the harmonic source of concern in the case of background harmonic voltage fluctuations

the kernel estimation with the partial linear method is researched and applied. To calculate the background harmonic voltage

it is expanded in accordance with Taylor series at a certain moment in the time interval of concern. And the higher-order term is regarded as an error term. To ensure the accuracy of calculation

on the basis of the least sum of square errors

the objective function considers the effective neighborhood of the moment and the influence of different error terms for different weights and uses the bandwidth to control the range of neighborhood and the size of weight. A case study based on an IEEE 14-bus test system is conducted to show that the method is more effective in comparison with two linear methods.