Identification and Mitigation Method of Harmonic Resonance in Offshore Wind Power Systems Based on dq-Domain Modal Analysis

Harmonic resonance challenges have intensified in modern power grids, primarily due to the high penetration of converter-based offshore wind energy. Traditional modal analysis methods conducted in the abc reference frame are often constrained by complex coordinate transformations and laborious analytical procedures. Therefore, research into dq-domain modal analysis and mitigation techniques is essential. This paper first elucidates the limitations of conventional modal analysis and outlines the fundamental principles of the dq-domain approach, validating its effectiveness through a three-bus test system. Subsequently, a resonance analysis model for offshore wind systems is established to derive the complete nodal admittance matrix. A dq-domain resonance analysis is then performed, and resonance is mitigated by optimizing the control parameters. Finally, the proposed dq-domain modal analysis method and suppression strategy are validated using a laboratory-scale experimental testbed. The results indicate that the proportional gain of the power control loop (KPP) significantly influences the system’s resonance modes. Fine-tuning controller parameters via modal analysis provides an active, flexible, and cost-effective solution for resonance suppression.