Resonant Frequency Analysis of Dual Inverter-based Resources with LCL Filters in Offshore Wind Farm

Abstract

Large-scale wind farms have emerged as a highly promising method for generating renewable energy due to their efficiency and usability. However, the power-converting process from wind turbines to the main grid introduces harmonics, necessitating the installation of harmonic filters as essential components. Among the various types of passive filters, the LCL filter has gained widespread usage in wind turbine integration. When applying an LCL filter, harmonic impedance analysis is significant for parameter design. Nevertheless, when implementing LCL filters in large-scale offshore wind farms, resonance issues may arise due to the presence of numerous parallel-connected switching devices and complex undersea cable connections, leading to unpredictable resonant points. This paper focuses on the analysis of the harmonic impedance interaction phenomenon of inverters, employing a dual-infeed wind turbine model. By deriving equations pertaining to the resonant frequency for an equivalent circuit of the system, the effects of resonant point variations were investigated. The simulation results provided validation for the calculated findings.