Harmonic Resonance Analysis for DFIG-based Offshore Wind Farm with VSC-HVDC Connection

Harmonic resonances can happen in DFIG-based Offshore Wind Farm (OWF) via VSC-HVDC integration, thus induce large current or voltage distortion and may risk system stability. In this paper, analytical impedance models of VSCHVDC converter and DFIG-based wind turbine generator are derived. Instead of studying system resonance characteristics through Nyquist method by equalizing a DFIG-based OWF and its VSC-HVDC link as a source-load system, the investigated system is treated as a multiple nodes network, and modal-based Resonance Mode Analysis (RMA) is adopted. Potential dominating resonances of the investigated system are analyzed, and the contribution of grid buses to each resonance mode is clarified, which provide reference for the design of harmonic filtering and resonance damping schemes. Numerical simulations are carried out to demonstrate the impedance modelling and RMA analysis results.