This thesis presents the stability-analysis results of a system composed of two offshore wind farms (OWFs) connected to two onshore power grids through a multi-infeed high-voltage direct-current (MI-HVDC) system. The OWFs are based on doubly-fed induction generators (DFIGs), and the MI-HVDC system is based on voltage-source converters (VSCs). With the focus laid on the influence of the common tie line in the MI-HVDC system, small-signal stability and transient stability are analyzed by utilizing system eigenvalues and time-domain simulations, respectively. The simulation results show that a VSC-based MI-HVDC system can be more stable than two VSC-based HVDC links which operate independently from each other. In addition, the stability of the studied VSC-based MI-HVDC link can be significantly influenced by the electrical parameters of the common tie line.

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