Novel Method for Estimating Utility Harmonic Impedance for a Direct-Drive Permanent Magnet Synchronous Generator Wind Farm

Accurate estimation of the utility harmonic impedance is significant for harmonic control and responsibility division. Traditional methods of estimating the utility harmonic impedance are valid on the premise that the harmonic impedance on the wind-farm side is significantly greater than that on the utility side. However, with the installation of filters and reactive power compensation devices in wind farms, traditional estimation methods are no longer applicable. The accuracy of most existing estimation methods depends only on the accuracy of the model. This can cause large errors in the estimation of the utility harmonic impedance on a wind farm. To address this challenge, this paper proposes a method for estimating the utility harmonic impedance for a direct-drive permanent magnet synchronous generator wind farm based on a modified model with measured data. The proposed method uses the measured data to modify a model to obtain a more accurate estimation of the utility harmonic impedance. The results of the simulation and case study indicated that the traditional estimation methods have large errors when the background harmonic fluctuates significantly or the wind-farm-side harmonic impedance is smaller than the utility-side harmonic impedance. In contrast, the proposed method has a higher accuracy for the above scenarios.