Analysis on Harmonic Resonance of Offshore Wind Farm Transmitted by MMC-HVDC System

This paper aims to investigate the internal harmonic resonance problem in offshore wind farm, when transmitted by modular multilevel converter based HVDC (MMC-HVDC) system. Firstly, the harmonic impedance model of components in the offshore wind farm transmitted by MMC-HVDC are built, including the impedance characteristics of the squirrel-cage direct-drive wind generator (SCDDWG) and the MMC station. Then, the analysis method on the harmonic resonance is introduced, especially the modal analysis method. Finally, taking one planning offshore wind farm in China as example, its harmonic resonance characteristics under different operation conditions are analyzed based on the modal analysis method. From the case study, it is concluded that the resonant frequency in offshore wind farm is mainly related to passive components such as submarine cable, and varies with the change of operation condition.