Improved Online Insulation Identification of Cable in DFIG-Based Offshore Wind Farm based on Harmonic Resonance Frequency

Currently, DFIG-Based offshore wind farm is mainly connected to the power grid via AC cables, and online identification of cable insulation condition (CIC) is crucial for the safe delivery of wind power. A method has been proposed to estimate the CIC based on resonance frequency analysis, but it is difficult to be applied effectively because it cannot take into account the influence of the power grid harmonic impedance on the resonance frequency. As a result, this paper improves the methed by adding prior information through harmonic impedance estimation. Firstly, the harmonic impedance of the power grid is estimated online by using harmonic measurements at the point of common coupling (PCC) of the wind farm and grid, and is used as prior information for the CIC identification, then the relationship between the resonance frequency of the wind farm system and the insulation condition is established, and finally the CIC is determined according to the measured resonance frequency. Simulation case verifies the effectiveness of the proposed method.