Dynamic Phasor-based Stability Analysis of Multi-Terminal VSC-HVDC Links with Offshore AC Networks

The paper proposes the stability analysis of an offshore wind power plant connected to an onshore AC grid through high voltage AC (HVAC) and multi-terminal high voltage DC (MTDC) transmission systems. Dynamic phasor (DP) technique is used to derive the small-signal model of the entire system and to analyze the system with sufficient accuracy and relatively lower computation cost. The DP modeling accounts for the voltage source converter (VSC) models, inner current controller, outer voltage controller, and droop controllers. The impact of the variation of the frequency droop gain, voltage droop gain and line inductance values on the system stability is studied by performing an eigenvalue analysis of the combined system. Simulations in MATLAB/Simulink are used to validate the DP-based analysis of VSC-HVDC systems for offshore wind farm applications.